yep, not a regular mopar input. all the A-body extension housing i've ever seen have the 307 bearing, even the 68 hemi A body's. long as you have a A-body extension and mainshaft you can swap it into a hemi box, even if its from a 23 spline. i don't know what the hell they were doing with the levers...
could be a hemi box somebody ran in a chevy.
you should pull the side cover and get a picture of the inside.