Once upon a time, a friend and I rescued a '52 Plymouth from an older lady's back yard. Got it running pretty easily, too! This was in about 1975. I asked the old-line Chrysler service manager at the local dealership what other engines would fit in that car. He said "pretty much anything Chrysler builds" (at that time). Consider, too, that the similar Dodges had Gen I Hemis in them, which had the A-motor bellhousing pattern, plus later LA-pattern. With that being mentioned, look at what it would take to put a Gen III Hemi where an LA motor used to be. And I believe that Holley now sells kits for A/B/E-bodies to do the Gen III swap.
Consider, too, that when the first Gen III Hemis were shown at Mopar Nats, they had a normal 4bbl intake on them, available from Mopar Perf, back then. With a normal distributor in it, too. As the earlier ones had 2 plugs/cyl. One set from the distributor and the other from the ECM? End result, a modern self-learning EFI and performance distributor could complete the deal? OR let the newer EFI unit control the ignition timing, too! THEN, all you would need is way to control the 8-speed ZF/TF transmission.
MIGHT end up being easier than you might suspect!
Enjoy!
CBODY67