Dont know how you could use a "modified" T5 with a 350 and not with a 327, sbc's from 65-99 (excluding LT1/LT4) are pretty well the same with the exception of different bores, strokes, and bearing sizes, then the addition of the 1 piece main seal in 1986.
LT1/LT4 are still pretty much the same engine, its just been changed around a bit to improve things, the transmission from any sbc that isnt a gen 3 + will bolt to any other sbc, and a bbc for that matter, it all comes down to getting the correct flywheel.
Using a 2 piece main seal block and crank would require you to get an aftermarket flywheel if using an LT1 T56, you can also change the input shaft, front plate, and bellhousing on an LS1 T56 and use it the same.
However destroking a 350 to 327 or 302 ci isnt going to gain you anything other than less power for the same parts, sure it worked for some stuff back in the day when they didnt have half the technology and parts we have today.
Though if you are dead set on small displacement and dont want to spend a lot of money, get an L99 4.3 crank from a caprice at a junkyard, the L99 is a mini version of the LT1, the crank is the same 3" stroke as an older 302, however you can use it in any current 350 block that has a 1 piece main seal, allowing you to use an off the shelf 93-97 T56, you will also need the rods from the 4.3 as they make up the difference for the stroke of the crank allowing you to use standard 350 pistons.
qwarnon wrote:true.. i would need some type of transmission adaptor. and yeh i know about 350 and 400 turbos.. those are rock solid.. but id really rather have a 5-spd... which i didnt think about.. with a 350 i could use a modified t-5 transmission... but with this 327 id have to find something else....