Being that the 223 has it's own unieqe pattern at the rear of the block for the bell bolt-up, I would guess that it would be a fairly easy exchange. I am not an Automatic Trans guy and do not have much of an idea what other concerns you may run into such as if your column shifter linkage setup will be compatable. There are other things to consider when making a switch from stock besides whether it will fit. Some of the Auto trans back then were Air Cooled, Some used the 'cooler-in-the-bottom-radiator-tank, and some used a heat exchanger setup, so you have to be careful what you are getting in to. You may or may not have to have your driveshaft redone. Just a few things to consider.
Fred