Modify your original frame with updated suspension, rear end, engine, transmission and brakes. Lot's of info on this site regarding the plusses and minuses with these old trucks. You can slowly modify it as you drive it too. Add disc brakes, install an open rear end with gears that you like etc. Lot's of bolter's use modified mechanics with their trucks, Cletis puts a lot of miles on his slightly modified Suburban and I am going a similar direction, but it's still in the building stages.
Check out
The HiPo shop you can see what others have tried and/or are working on.
