I believe you...as far as I know they offered 351M/400's in 82. It would be cheaper for you to stick with the same family engine if you want to do a swap: 351M/400/351C are "335's" and the 429/460 are all part of the "385". They have the same bellhousing patterns and will all use the same frame towers, just different motor mounts will be needed. I've seen 351M's and 400's dirt cheap and since you admit that you're not really a Ford guy, I'd just find a running 400 and throw it in.
That being said, if you want more performance, go the 460 route. I swapped my 351M for a 429 in my 77 F150 and it wasn't very difficult at all. Just keep in mind that parts for Ford BB's are not like SBC parts (cheap).
If I understand the question correctly regarding the bellhousing coming off of the tranny, the answer is "No". The C6 auto is an integral cast bellhousing and is not removable so therefore you would need to find a tranny with the proper housing for the engine you want to run it with. I'm a manual guy so don't quote me on this but there are three housings that I know of: small block (289,302,351), FE (360,390, 428), and 335/385 family (351M,400,429,460).
Removable bellhousing...that would be too easy.
