1966 C1000 cab repair panels

[malice]

I've started the restoration of my 1966 C1000 and am currently working on the driver side replacing the cab floor (includes the inner rocker), the lower portion of the 'A' pillar, the outer rocker and footwell panel. Replacement panels specific to a '66 GMC are easily obtainable however…they're not fitting as advertised. I'll try my best to explain what I'm seeing and hopefully someone here has come across this and knows what I need to do.

The original front cab support has 6 bolt holes which the cab floor, footwell panel, the 'A' pillar and the rear mount for the front fender all bolt into.

Cab floor - the 3 forward holes are supposed to line up with all 3 holes of the fender mount. The middle and bottom holes line up perfect but top hole is about 1/4" too short…and the front edge doesn't meet with the firewall quite right.

Footwell panel has 3 holes. The middle and right holes line up perfect with the cab floor and the left hole lines up with the corresponding fender mount hole. So the spacing between the middle and left hole of the footwell are correct but the corresponding holes in the cab floor are not. Don't vendors know that the holes of all 3 pieces (fender mount, cab floor and footwell) are supposed to align?!!

'A' pillar replacement piece - the original has 2 holes on the left and 3 on the right; the replacement has 3 on the right but only 1 on the left. It's not difficult to drill another hole but it doesn't match the contour of the pillar either. It is twisted to face slightly backward where the original is not. I was able to twist it straight and I think it will work but I shouldn't have to do that for a direct replacement part.

Outer rocker - I can see the bottom is not going to line up with the cab corner but I haven't worked with it enough to speak to what's wrong yet. Being the most visible piece, I sure hope it's not too far off.

The footwell piece works and I can accept the 'A' pillar piece, but the cab floor…that's cutting, reshaping and welding which is not something I should have to do for direct replacement parts. I've tried 3 different types of replacement pieces from 2 different vendors hoping they'd fit different…they don't.

Am I seeing the difference between Chevy and GMC? I wouldn't think so since the pieces are sold to replace both Chevy/GMC applications. Or perhaps the difference between standard and custom cab? I suspect I have a custom cab but, from what I've read here, the only difference is in the trim…or maybe not?

Sorry for such a long post but hopefully my explanation is clear. Any insight and/or direction would be much appreciated! Thank you in advance.

[AZKen]

I see you are new here. I don't know if you are new to patching or these trucks in general.
1. Most panels are made by China. Most vendors use the same Chinese supplier.
2. Most panels need tweaked slightly or a lot.
3. They are made from tooling that was designed from perfect examples to fit a perfect truck. All tooling gets worn.
4. They get packed tight for the long boat trip. Handled many times by many people and machinery. Which reshapes them.
5. Our trucks have many miles on them. Twisting, rolling, stretching, overloaded, heated and frozen.
6. Most have been in a collision or five and have repairs by all manner of owners and garages.
7. Some have had home made patches, welding, hammering and rube fixes.
8. If you are looking for an answer, there is none (see *). If you are looking for someone who's had the same experience. Everyone has.
9. Innovate, hammer, drill, cut, reshape, slit, cut in two.........make it work. You get better at it over time once you get over the shock of not fitting out of the box.
10. Sometimes during a fix like you are doing, the sequence is VERY important. Bracing is necessary. Sometimes the cab gets "released" "relaxed" when cuts are made. This will add to the patch fit problem. You may not notice that geometry has changed. Dimensions changed. The patch gets blamed. If you cut out the floor and inner and outer rocker and etc., all at once, you will definitely loose geometry.

Most patches are way closer to shape than you could make yourself and cheaper.

* Donor pieces will be better most times, albeit very hard to find someone willing to cut up a truck cab.

[malice]

Thanks for the reply AZKen. I've had the truck for 28 years but am not as familiar with the differences between years, models, options etc. as I suppose many others here are. And yes, patching is new to me.

Regarding #8 - I was hoping to find someone that has purchased these panels and can confirm whether they fit on their '66 GMC (with a little massaging, of course). Someone to answer whether the panels I'm getting should fit. If so, I'll know I'll be fabricating the correct piece to fit my misaligned truck versus the wrong piece for my perfectly straight truck.

Some of what I'm seeing makes me think these pieces are not for a '66 GMC...or there is something different about my cab. One piece I tried spans from the inner rocker to where the transmission hump bolts would normally be*. The contours around the gas petal and the little 'gutter' in the center of the floor matched but the cab mount hole didn't line up. How can multiple contours of a stamped piece align perfectly but not have the cab mount hole in the right spot? Or have a curve where it meets the firewall when my firewall is perfectly straight. I can understand a little twisting and tweaking as part of shipping but not differences like that.

*My floorboard is without a transmission cutout - its all one piece.

[AZKen]

Provide vendor and all part numbers that you bought. There are floor differences for 60-62 and 63-66.


Also, this from the Jolly legacy page under "Chevy and GMC differences":

"Most All body parts will interchange between the trucks of this era. Some my
require drilling of new holes, like for Grill. Cab Mounts will differ from
Chassis types, Years & Series of trucks. Most can be used with little work."

A major change was made to the windshield/door design in 1964.

You may have to make a judgment call. Figuring out the least modification to make. I.E. if everything lines up but the cab mount hole, that's the one to plug and re-drill.
Do you have any of the old floor panels? If so, SAVE THEM!!!!!!!!!!

[malice]

From LMC:
38-8982 - Outer Cab Floor Ext-Left Hand - Chevy GMC 60-66

From Brothers:
RFPS650 - 1960-66 CHEVY/GMC TRUCK CAB FLOOR OUTER SECTION - FULL
LEFT

FRP6366 - 1963-66 CHEVY/GMC TRUCK FRONT FLOOR PAN - ORIGINAL DESIGN
LEFT


The outer cab floor piece 38-8982 from LMC and RFPS650 from Brothers were identical. The half floor piece FRP6366 had the same alignment issues at the A pillar and firewall. Looks like 38-8974 is LMC's version of the half floor which perhaps I'll try but its most likely the same as the one I got from Brothers. Either way, that might be the right piece to fabricate into place.

I'm only replacing these pieces because what I have is rusted out...there's nothing worth saving.

[AZKen]

I think you are getting a good handle on what is available and how to plan the repairs. As we would all have to do. Good approach.

Get the parts, lay them over the area they go and think on it.

The general idea is not to cut out more than is necessary, Not to use any more of a patch panel than is necessary. You may have to brace the cab so it does not move when things are cut. Take many measurements before starting.

Watch this.

[malice]

Good news for anyone else struggling with this same issue...JEGS part number 576-0848-217L for the driver side floor pan fits pretty good. The cab mount hole doesn't line up and there is no 90 degree bend for the firewall seam but those are easy fixes compared to what any other "direct replacement" piece I received would need.

[AZKen]

I don't know if you are saying other floor panels you got did not fit. If you are, something does not make sense here. That Jeggs piece is the same piece that everyone else sells. Made by the same Chinese company. The Brothers, LMC, Jeggs, American Classic Trucks, Etc....all the same. They all sell a "universal" one and an "OEM" one.