The tail housing bolt pattern, spline count and shaft size are completely different on the output of the a650e. The a650e is plated to handle 350 horsepower and is a much nicer transmission to drive however. Mr DesJardin has a new shifter that would work well with it allowing you to use the switched first gear selection. There are several possibilities to make it work all of which are custom. I came to the conclusion that the easiest way as i was determined to use the a 650e) was to use a divorced atlas of some description. Then having done weeks of research decided LS, domestic tranny with an atlas bolted to the former was the easiest most sensible way to go.
Edit:
the A650E and the A750E are not alike in any way.. the overdrive one way clutch is external to the main casing in the tail shaft housing whereas the a 750e is internal iirc