[jimjaz]

Hey PLYONS11,

Swapping out a 63 GMC front end to acquire 5 lug disc? I think I can help you out here with some specifics and thoughts for you to contemplate. I have done this swap on my 65 GMC Sub which was pretty straightforward since my 65 has a mechanical clutch linkage and bell crank. Your 63 uses a hydraulic clutch, right?, so you have two lines off your master- one for the brakes to all 4 wheels, and the other for the clutch. To me, this will most likely be your biggest hurdle. If you can convert your hydraulic clutch to a mechanical setup as is used in 64-66 GMC trucks, then this will make things a whole lot easier for you.
I used a 79 GMC (or Chevy front end- it doesn't matter)- all 73-87 GMC and Chevy trucks are all 5-lug for the 1/2 ton, which is what you are after.
Go out to your truck and take a peek at what is hanging down the lowest on your truck. Is it the oil pan? Doing a drop spindle thing like 4 inches won't work- you will wind up tearing a hole in your pan, and if you don't know, the big V6 can be very expensive to repair/rebuild/machine/buy parts for. Don't go here, please! A guy in Chandler AZ was going to do this and was saved by Chris out in Apache Junction AZ who told him, "You can't drop slam your truck from 1/2T stock with a GMC BB V6. Your oil pan will then be the lowest thing under your truck." The V6 weighs in at 825 pounds carb to pan with exhaust manifolds. A SB V8 is about 500, BB V8 only adds about 50 pounds. You need to think on this as well. 825 lbs over a half-ton conversion kit from CPP or ECE or wherever with or without a 4-inch drop will most likely make you very unhappy due to bottoming out even on bumps and road divots that a stock suspension would more or less glide right over. The aftermarket houses job is to sell you their kits, their parts, and they are probably not going to tell you that their stuff is just not built to take on an 825 pound engine over the front wheels. Bottoming out is REALLY hard on front-end stuff.

My conversion on my 65 was a 1/2T to 1/2T, kept my original springs and marked them side specific (they have the natural 53 year drop on them), and I like the ride height and use mine as a truck to do truck stuff like going off road to camp, fish, haul firewood, and what-not. Doing any drop spindles is rather permanent and you are most definitely going to limit where you can go; road humps and street to parking lot curbs will be your enemy, even the moderate ones. Air bags are out, since you would need to change a whole ton of stuff for the rear that you say is pretty much done, and then there's the oil pan thing. I just mention this so you can think about this "down the road" (excuse the pun) before you take the plunge and have many regrets. Nobody wants regrets.... On to the meat and potatoes....
- both my 63 GMC Sub cross member (came with V6) and my (now) 79 cross member in my 65 (came with an I-6) have the same mounting hole pattern for engine mounts in the cradle between the frame rails, and both have 3 holes on the top of the frame rails, each having 2 and 5/8th inches center-to-center spacing. Yours should be no different. In essence, these 73-87 cross members are the same as 60's stock which makes them very versatile.
Here is the skinny on my findings when I did my 65 (factory drum front) to 79 factory disc front) conversion;

First, the bad news- you will have to drill one hole on each side of the frame to accept the later year cross member, and you will also need to elongate one hole on each side that do not line up directly, sort of like a half-moon affair. Your template to do this is already there, since there are already holes in both the cross member and your frame that DO line up directly. Just put in the bolts that line up, then drill one and elongate the other.
Also, kit parts are only available from kit vendors, so you are basically married to them as long as they manage to stay in business. I do not recommend a kit from anybody for this reason- everybody and their mother sells OEM stuff for GM/Chevy trucks. In other words, your options are pretty limited.

Now, for the good news, and there is lots of it (using OEM);
- 73 to 87 cross member is compatible with the same engines that 60-66 GMC and Chevy use. The V6, V8, or I6.
- the 1/2T donor truck will also come with coil springs already broken in. They are going to get you a softer ride than your current 3/4T setup. The V6 being 325 pounds heavier than a 73-87 with V8 will probably get you a 2-inch drop up front just from the mass of the V6. If you happen to remove the springs, mark one and put it back on the same side it came out of. Springs are funny and don't "wear" the same. If you get them put in backwards, then your truck could be listing to one side.
- donor truck comes with 5 lug spindles that you want.
- bigger, beefier upper and lower ball joints. The ball joints on our 60's 1/2T trucks are wimpy in comparison.
- OEM 73-87 spindles are far superior to any aftermarket "kit" that adapts front disc using your 60's factory wimpy ball joints if you were going with a "kit". You will not be happy with a kit, in my own humble opinion.
- if your 63 truck happens to have factory front anti-sway installed, then good! A lot more 73-87 GMC/Chevy trucks already have this. Much thicker bar, so much better resiliency to sway. Get the anti-sway from the donor truck anyway, but be sure to get the frame cradles as well.
- factory A-arms (zerk greaseable) would be a better idea than going with the poly bushings for A-arms. They will creak and squeak over time. This alone causes folks to stop going to car/truck shows from the weird noises it makes over time. Tubular A-arms? Why? Nobody looks at them anyway.... is there a benefit? I go back to the V6 sheer mass and weight to say probably not a good idea.

My 1965 GMC Suburban swap is all OEM using a 79 non-power brake front end and all the associated components that drop out with the cross member (A-arms, springs, spindles, rotors, and front spindle soft brake lines that come off the outside of the frame), and got the front hard brake lines along with the master cylinder, prop valve, and anti-sway bar. I did not want a power brake setup for reasons of the potential to lock up your brakes during a panic stop ((( oops! Too late, you are already headed sideways...))). The exception would be to have anti-lock brakes installed, and that is just crazy expensive and a whole different ball game. 75 to 80 percent of your braking is done up front on the disc rotors anyway, so doing my all OEM conversion to disc/drum was easy since the 73-87 trucks are all this way. Have you thought about this at all? Power brakes are simply not needed if the disc/drum braking system is designed properly, and GM has done tons of design, testing, and engineering on braking systems, and this is the main reason for me going with OEM versus aftermarket since GM already did the work. My conversion was kind of a no-brainer- yours is going to be a challenge because of the hydraulic clutch you currently have. In your case, you cannot, to my knowledge, use a master cylinder except for the one that came on your truck. Have you mentioned this little factoid to CPP or ECE regarding the kits they sell and compatibility for your hydraulic clutch? This is uncharted waters for me. This would require a 3rd output line off the master since 73-87 disc/drum braking systems use a master with two reservoirs- one for the front and the other to the proportioning valve for the rear, or you could potentially find the 64-66 GMC mechanical clutch linkage stuff with bell crank from somebody on the site or salvage yard that just happens to have all the stuff which would solve this problem for you. And just remember you would need the frame side piece as well for the bell crank. This is factory riveted in place on the donor truck and not just bolted on. This is a critical component if you are changing from hydraulic clutch to a mechanical linkage and you must have this part for your frame rail as well, otherwise you got nothing that will actually work. I can't imagine that the block on your V6 would not accept a bell crank adaptation, but you would need to verify this before proceeding.

My advice to you is to seriously think about staying with OEM using a 1/2 ton donor truck 73-87 that will have almost everything you need, and start out with the stock spindles. Do the swap with everything you can get off a single donor 1/2T GMC or Chevy truck for one cheap price- the entire front suspension that drops out via 6 or 8 bolts that hold the cross member in place, and the other stuff already mentioned. This is ALL based on you being able to find the parts to convert your hydraulic clutch to mechanical linkage, and (more bad news) THIS WOULD INCLUDE THE BELL HOUSING off of a 64-66 GMC that would need to be changed out as well. The hydraulic is passenger side for release bearing pivot fork, and mechanical is driver side. You could get everything you need from just one truck if it were a 64-66 GMC with a BB V6 in a wrecking yard. This is going to be easier said than done.
I know this is very windy and long (and boring?), but I do hope that it may give you some better direction or a different way to go. My way is most certainly not the only way....

Regards,
Jim