R Pope is right on with this. If you have a stick (sounds like it if you're talking bell housing), it shouldn't be too big a deal. More info would help - type of trans, mostly. 352, 390, 410, all the FE engines should drop right in, but you'll need to make sure you have the right bell housing. Various sources for these - I've done well with Bob's F100 in Riverside, CA, but there's John's F Fun Hundred in Orange County, and any number of other sources.

Mac's produces a catalog for these, as does Auto Krafters. Auto Krafters is on the East Coast, but also have used parts. They're at 1-800-228-7346 (just got a new catalog, and it was on my desk).

Good luck. Should be an interesting project.