The problem with merely replacing the case is it won’t solve the problem. Magnesium cases are soft; aluminum pumps are harder. The problem leak will come back. Maybe on someone else’s watch, but surely you pride yourself in fixing problems.
Save your customer money and fix their problem the first time with this simple drop-in:
1) Clean case and repair damage with an epoxy or you may choose to have welded.
2) Place BRNY protector in the pump pocket.
3) Continue the rebuild knowing it’s fixed.