Early A Body Steering Column Interchange?

The answer to the question is pretty much yes, provided you understand that manual steering shafts and power steering shafts are different lengths (housing is the same) and that the terminals on the turn signal wiring are different 63 to 65 (can't remember if just 63 is different or not). But it's easy enough to swap turn signal wire harness. Or to cut the ends and swap wire terminals. I swapped turn signal harnesses when I swapped columns between my 65 Barracuda and 63 Valiant. (One had a PS column and the other a manual column; I needed to switch which one had which.) Other than the turn signal harness, they just bolted in, from one to the other.

Edit: just remembered you also have to swap the firewall plates as they are not the same.

I'm pretty sure you could also swap shafts from one column housing to the other, if you have PS and need manual or vice versa.
Thanks for the info. Good to know about the firewall plates. I was going to use the harness out of the 65 Dart. I can make that work. More concerned with bolting it to the dash and firewall and steering shaft. Thanks!