Bell housings.... school me please

Had a 4sp in a 69 Road Runner. Seriously thinking about making my 68 B'cuda a 4spd. I'm already dead set on gong big block. I have a 383 block and 440 guts that will make a nice low deck stroker. As far as the bell housing...... I've seen the scarce A body big block bell offered up for sale, and have found several big block bells locally from B, C and truck bodies.
Not so worried about the trans. I'll grab an A body 833 trans easy enough.

What are the differences in the bell housings?