After examining the back of the 360 crank I have determined that, yes, it is indeed incompatible with my transmission torque converter in the 904.
<snip>You can buy a 72 360 flexplate and bolt it to the 70 crank. NO NO NO! This is totally wrong! You cannot bolt a late model (727/904) flexplate to an early (BorgWarner) crank! You're getting bad advice here! The flange mountings are different, and they won't align without adapters.
The rule of thumb is easy: in 1972 everything changed. In general, you can't match pre-1972 engine/trans with 1972-up engine or trans. There are allegedly adapters for the V8s (I have no experience) but if you want to cross that boundary, it absolutely requires careful research and probably modifications.
I now have three nice bellhousings (1963, 1969, 1972+) and one of them is double-drilled, and I'm going to make drawings of the patterns (both sides) for ID and comparison. Don't hold you breath but I will do it.