If you can come up with a stock II bell, I think a T5 would be a fairly easy swap. It would probably need all of the updates/modifications that installing one behind a 302 would and should work with a stock clutch setup (If you're still able to get them for the V6?). Another option might be getting a bell from a 4.0/T5 combo out of a later model Mustang. To the best of my knowledge they are the same engine architecture, but I can't say for certain if the bell housing bolt patterns are the same. I don't know of any other manual transmissions that swap in as easily, I've only done the T5 in my Cobra....