4 speed b body to a body

The B 4 speed is same length as a 727, the A 4 speed is same length as a 904. So, length is not "the" big problem. The big problem is the location of the shifter mount pad, or pads in the case of a 70 / later B/E gearbox. There is a diagram, floating around, somebody made an adapter bracket. I have no idea what that might do to the "floor plan."

Here:

http://www.bigblockdart.com/techpages/techindex.shtml

which leads to

http://www.bigblockdart.com/techpages/abconv.shtml

However, the earlier "B only" gearbox, with only the front mount, would be harder, as it's in the road of the crossmember