far as i know there is no overdrive auto that will bolt onto any AMC motor, 6 or 8. engine was made before that era. a couple of manual ODs but you don't want those unless you like boatanchors (i drive one :-)

the wikipedia page for AMC sixes is pretty good for an overview if you dont know it. block rear mount face radical change in 71, so post/pre blocks and crank butts not interchangable. bells changed then.

there's a thread on the AMC Forum http://theamcforum.com Transmission section about adapting some Jeep OD auto, but its gonna mean some milling.

on the whole AMC Forum is is a bit fuddy, concerned with ekeing out a few more miles from Betsy, and do i need a new carby-retter?

Frank Swygert shows up here in inliners once in a while, knows a hell of a lot about AMC, and publishes a magazine about them.