I'm finding there are 4 hex bolts which hold the pump to balancer4 small Allen head cap screws
No I'm talking about the impeller housing bolts3/8-16 thread size going into the SBC balancer
take one of your existing bolts into your local NAPA or Ace Hardware
Yes didn't want to remove one of 3 left inyou mean the little M4 or M5 screws?
take to your local ACE and find.