Are rear main seals interchangeable between LA and Big Blocks?

Kern Dog said
Oddly, the 360 crank main journal is stepped up in size at the oil seal area. Why???

No idea but yes. Also the 360 oil pan is different than the 273/318/340 because of the same reason.
Next one I do will be getting a rope rear main. Chrysler was still using them well into the late 80's.