It has to be '66 or later (& in '66 it was called the Cruise-O-Matic C6, carrying on the old Cruise-O name for one year more....though it shares nothing in common with the true Cruise-O-Matic). Full-size Fords- LTDs, big wagons, etc. '66-'71 are a good place to look....lots of 390s and almost always automatics. The '70-'71s are more likely to have 400s or SBFs. The intermediates- Fairlane, Torino, Ranchero- sometimes have them through '69....but have often been stripped already. Mustangs-same thing, but you can try '67-'70. T-Birds- '66- early '68. Trucks- '66-'76; again, lots of 352s, 390s, & later 360s, many with autos, more so in the '70s. The FE was dropped from cars after '71 & light trucks after '76. The same thing applies to the corresponding Mercurys. Lincolns will do you no good as they used the MEL in '66-'67 & the 460 from then on.
Yep. If absolutely necessary, a slip yoke-type rear shaft & different tailhousing can be installed from a different C6 (doesn't have to be FE). You do have to disassemble the trans. Not particularly hard, though.