manual to auto swap what will work?

I am thinking about keeping my slant six until it dies and then swapping to a V-8, although I have all the parts to do the swap. I just cant bring myself to pull the old six becuase it runs so well, but I want to swap my 3 speed manual to an auto in my 65 Dart. Will I have to find a 65 model automatic or will a later model work? I would like a non push button tranny is this possible with the location of the starter on my 65? A neighbor has a auto tranny for a slant six out of a 77 Volare would it work?
Thanks in advance for any and all help.