As the title says, I had a coolant leak from the water pumo housing and think the cause is that the raised lug on top of the front iron for the stud has cracked in half and the top piece is missing, is the anyway to repair this or could I just drill the hole deeper and tap it?

 

The aluminum housing? If the housing is cracked I would replace it with a new one which should be available as the housing may continue to crack farther. $325 for a complete water pump assembly is far less expensive than an overheated engine.

https://www.atkinsrotary.com/store/8...0-15-010A.html