Tremec t-5 would break almost immediately behind a 340 but he said it's not that so that's good.
TKO is a good trans but it's big, be ready for lots of fab time and cutting out the trans hump/making a new one or spending the $$$ on panels.
TKX is a newer trans and it's compact, I believe it should "fit" with minimal mods but may still need custom parts such as a crossmember (maybe)
As you can see it's important to know which one you might get because they're radically different to swap/make work