Will,
The interesting question to me is how could this happen? Something not right with the contact between pump lever and the pump lobe on the cam shaft. I'd want an answer before I put in a new pump. Did you compare the new pump with the old one before you put it in? Since you didn't change camshafts, I would suspect that you didn't get the right pump. Did you put the bakelite spacer in between the block and the pump? If the broken off lever fell into the sump, you could probably just leave it there. Try to snake one of those little magnets on a gooseneck in through the oil drain hole. If the broken off pice is small enough, you might be able to get it out. Drag a magnet along the bottom of the oil pan toward the plug hole to see if the piece is there and in the lowest part of the sump.
Good luck,
Bob S.