Any transmission from the sixties is good, and can be built as swing axle or IRS. They all have side covers on both sides of the transmission.
I don't remember the changeover year, somewhere between '71 and '73, but after then the transmissions were dedicated to being IRS, and rear wheel drive only. The transmission cases only had one removable side cover for installing a differential. It only went in one side and the other fixed side(part of the case) only accepted IRS flanges/bearings.
All the DSC(double side cover) transmissions could be built for RWD or mid-engine, a simple matter of installing the ring gear from the other side to swap drive direction.