Do not know why there are different part numbers, I assume the bullentins are OEM from factory.
From my experience all 3 and 4 cylinder Chryslers had 3,3126 bore std and the pistons 3,312 except for the 135Hp, 140Hp and 115Hp mid and late 70es that had 3,375.
I have a 135Hp 1976 and it has...