[slotard]

square body wheelbases:
Blazer 106.5"
SCSB 117.5"
Suburban 129.5"
SCLB 131.5"
Crew Cab 164.5"

GMT400 wheelbases:
Tahoe 2dr 111.5"
Tahoe 4dr 117.5"
SCSB 117.5"
Suburban 131.5"
SCLB 131.5"
ECSB 141.5"
CCSB 154.5"
ECLB 155.5"
CCLB 168.5"

While the 4dr wheelbase matches the SCSB, I know that on a square body the frame is shaped significantly differently between trucks and Suburbans. With the amount of work you're putting into the body I'd be tempted to just build a frame too, so you can do it how you want it (I assume boxed, set up right for links, etc)