I think the slickest swap would be a 318 or 360. You'd use the old bellhousing and the old bellhousing mounts, and everything behind the bellhousing stays the same. The LA motor is much easier to fit in there than a 440. The other thing is that your transmission is very likely a New Process 420 which is strong enough for a pretty stout 360 Your engine would need to have new mounts fabricated but they're pretty generic.

The Power Wagon guys have a lot of info on these older dodges.

The bellhousing in my '64 D100 has bolt holes for flat 6, Slant 6, and A engine which is same as the LA except for one bolt which you can easily add. Your '52 may not have the same setup for slant 6 because they weren't designed then, but it might have holes for V8.

R.