[Chuck78]

The front 5 lug disc concerns that I wanted to poke around this forum for were more along the lines of what front springs to use, as I'm going from torsion bar setup to coils. I really like the torsion bars and their adjustable ride height, but I still found them to not be quite stiff enough. I will miss that setup, but getting 73-91 Suburban / 73-87 truck interchange on replacement parts is AWESOME and worth the tradeoff. My ball joints are shot, and all 4 priced out 10 yrs ago cost more (nearly double!) than replacing every single ball joint, tie rod, idler arm, & bushing on the 73-87pu/91burb front end!!! Plus as noted, a better & more stout ball joint design...

Back to springs... the 89 suburban I had rode pretty soft up front with a heavier 700r4 trans and a much lighter and excellent 350tbi engine. I will be adding at least 250 lbs to the front end vs the 89 burb drivetrain. However I recall seeing the weight of a 60-66 1/2 ton 1000 panel being listed as 4,000lbs, & the 89 Suburban I had was listed as 5,000lb if I recall correctly.
(I NEED TO RE-VERIFY THESE #'s)

Let's assume that may have been a Chevy 1/2 ton panel weight, & say 4,300lbs on the panel. The 89 burb is much longer and has more interior trim and back seats. So 65% of that weight difference may be biased toward the rear. If all these figures are in the ballpark, that would mean the 89 burb springs are spec for about 245 lbs more weight than if ran in the 62 gmc 1000 panel.
This would seem like everything should work out fine, but I am very skeptical and I'm thinking that the much heavier GMC big block v6 engine directly over the springs is going to require heavier springs than the 1989 Suburban front crossmember has equipped stock.

I can drive the truck onto the scales at the scrapyard, & then get 2 additional measurements with the front wheels only on the scale and the rear wheels only on the scale, & likely could go to an aftermarket spring/suspension supplier and get a good spec.
For my prior 70-81 Camaro/Firebird hobby, I came across a chart of moog spring diameters/coils/wire thicknesses/heights/etc and picked some random oem replacement springs that were very close to the height I wanted and the rate of choice. That may take some research for the truck, or else find a 1/2 ton suburban 454 big block spec spring. Maybe even a small block 3/4 ton Suburban spring.