2 barrel to 4 barrel

There's a guy on the /6 site that has all early a bodies ("Dart 270"-- aka Lou Madsen) who's run an a500 and has since switched that car to a gm 200-r4 in that car, I forgot what he liked better about them, other than size/ which in and of itself wouldn't matter since he's had an a 500 in that same exact car for something like 10 years before he swapped.
If I was gonna get a different brand of trans i'd be going away from an automatic for a T5. which wasn't a Ford or Chevy trans, as much as it was a Borg warner no matter what body it was put into.... I've not done the swap but direct retrofit parts are out there, and I've heard room wise they leave plenty to spare.