What I'm trying to wrap my mind around is to why you keep losing time. Is it too far advanced or retarded? It sounded like the engine started right up for you when you installed the body? What is leading you to think that it is now out again? Timing light, or by ear?
Instead of pulling the oil pump every time you need to move the distributor a tooth, I would make a slotted piece of copper pipe that can be inserted to the oil pump drive to turn to match your distributor drive. It will take a little playing to get it to line up perfectly, because you'll have to figure on the distributor turning slightly when engaging the cam. In my mind it is better than tearing off the oil pump every time you have an issue.
The M38A1 was much better that the M151. The M151A2 wasn't bad after the rear trailing arms were modified to reduce the chance for the MUTT to roll over during a turn at speed. The picture is of how must M151s ended up.
