Wondering if when rebuilding the IP you could have reassembled it 180deg out? This came up recently on
another thread. The inner end of the main shaft has those two prongs, they are not really keyed, can fit either way into slots in the distributor. There is a specific clocking orientation where you visually align the key slot in the main shaft with a pin in the distributor plate, but it will just as easily install 180 out and rotate freely and not bind.
Suggest before swapping the IP, retime it 180 deg. out.