Can't say about 65. By 1966, Mopar recommended Mercon/Dexron III in their transmissions. It's cheap as ATFs go, and universally available. Take care to avoid Dexron VI which is formulated for GM transmissions and is too thin.
Of other ATFs out there, I plan to avoid Type F (for Ford C6). I've looked at ATF+3 and ATF+4 as it is marketed towards Mopar auto trannys. It's formulated for the new OD units. I have yet to see anything about anyone successfully using ATF+3 or ATF+4 in a 727 or 904. The instances I have read concern using the fluids in recently rebuilt units so the possibility of interaction between additive packages approaches zero.