Pilotpat

Hello. I built a '73 5.7 block up into a running motor for my first build. I've picked up an OBS truck with a 4.3. I want to use the accessory brackets from the 4.3 but the Alt/PS bracket has a bolt and stud that mount to the block at the bottom. The upper bolts have taps in the heads but my block does not have tapped holes for the lower two but does have what appear to be "Bosses or Pad's" where they would go. Q: Is it appropriate to drill and tap those locations for the bracket mounts. Thanks for any replys.
Patrick.