Stop in for a cup of coffee

A body VS B Body?
Actually, I almost wonder if you have found a slant 6 727… that would account for the differences as well.
Feel your pain Chris ( @dukeboy_318 )

Pulled the old transmission out of the car. The new one is NOT a 904...or at least it appears that the tailshaft housing is not. ID number on the transmission is a 65 Slant 6 HD Valiant and the housing accepts the pushbutton but it is several inches longer :BangHead:

So I'm a dolt for not recognizing that but everything from the bell housing back to that point is totally correct.

View attachment 1715999145

View attachment 1715999146

View attachment 1715999147

View attachment 1715999148

View attachment 1715999149

View attachment 1715999150
or you’ve found the rarer slant 6 727 pushbutton. That would account for the differences as well