How much horsepower/torque are you planning on making? I've heard of LT1 F-Bodies pushing 500 hp that are still using the stock T56. If you want to though, you could get a ZF6 transmission from an '89-'96 Vette. These are a little tougher than the T56 but are more expensive and harder to find. Right now, GM is putting them behind their 6.6 liter turbo diesel V8 that produces 520 lb. ft. of torque and 300 hp. It is also used behind the new 8.1 liter big block V8 that makes 340 hp and 455 lb. ft. of torque. Both of these are in the new HD Silverado. I don't think there are any major internal changes to the transmisiion from the Vette to the truck. Just a different case.
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1991 Z28 - 350 TPI, T56, McLeod street clutch, ported plenum & runners, AFPR, Holley Annihilator ignition box and wires, Hooker shorty headers w/o AIR, Flowmaster muffler, homeade ram-air, SSM subframe connectors, Kenny Brown STB, Global West steering box brace, Steve Spohn adjustable torque arm and T56 crossmember | 
