I personally would look for a 94+ SBC in a truck and grab the Vortec heads and pick up a new intake.
The Vortec-head (L31) 350 started in '96 and ran thru '98 in the trucks and '99 in Tahoes and Suburbans. '88-'95 used TBI with the low performance TBI heads. The difference is also, as stated earlier, different flexplate and balancer, and a one piece rear main seal.
A great upgrade is a set of Vortec heads, a GM or Edelbrock TBI vortec intake, Edelbrock shorty header & y-pipe kit (made a big difference on mine), and a little more cam (since you're going that far into it), like this:
HYDRAULIC-Great in throttle body, crossfire or carbureted engine and 305 TPI.
Hyd. Hyd. 1000 to 5000
12-249-4 XE249H
lift .434 .444
dur - 249 260, at .050 - 206 212
centerline - 112°
That would make a killer torquey street engine, and running it up on my computer dyno shows about 324 hp at 4500 and 423 ft lbs of torque at 3000-3500, and 421 ft lbs of torque at 2000.
I had an 89 Suburban 2500 with a TBI 350, and was going to do this to mine, but ended up selling it to a friend of mine (it had rust issues) and got my 04 Suburban 2500 with the 8100 BB and 4.10s. Good luck with it.
