4-Speed Swap Donar Car Question

Hello,

Apologies if this has been asked and answered before, I tried searching but I had problems phrasing it so it returned results.

I have a 1969 Barracuda with a 340 and I'd like to know what vehicles would work as a donor for a 4-speed swap.

Is it all '63-'72 A-bodies with a manual? Did the donor car have to be a 4-speed or can it be a 3-speed? Does it have to be a V8 car or will a slant-6 work (knowing that the bellhousing/clutch/flywheel/etc won't work)?

Any other limitations?

Thanks,

Mike