Thanks for all the info.I have had no luck finding a GMC engine.But a local wrecking yard,about the only one left with the old good stuff has a pretty much complete 48 1.5 ton.When I saw the engine,I thought it might work.But I may just end up going SBC.The extra ponies might be nice.Did'nt GMC have a V8 in some of their later trucks?Would it bolt up to the SM420 4spd? I came across a SM420 also that had a huge bellhousing bolted to it,and assumed it was for a GMC.