The ONLY difference in the engine are the 4 bolt mains on the Vette LT1 and the 2 bolt mains on the f-body LT1, and a SLIGHTLY different cam. The cam is not a big difference, and if I remember correctly it's actually a little smaller in the Vettes than the f-bodies, but it's so close that it shouldn't make any difference.

The power difference comes from a freer flowing intake (basically the same airbox as a ramair WS6/Firehawk), and a freer flowing exhaust (true dual 2.5", with manifolds that are similar to shorty headers). The TB is exactly the same. As for whether the HP diffence is true or not, my bone stock 92 LT1 Vette (M6) made 270RWHP.

 

I am pretty sure the TB's were 48mm. I know the 52mm fits the intake holes perfect though. It is the 58mm that you have to cut some off the intake holes.

Other than that, I am pretty sure it is just the 4 bolt main stuff, and of course, differently routed exhaust.

 

The C4 Vette uses a 48mm TB.

Aside from what has already been mentioned, most of the front engine dress is completely different. Even the water pump is a bit different. The opti should interchange though.