speaking of drilling out plugs.. there's a good trick hidden in that statement.
many times I have seen a stripped hole ina casting that I did not want to or could not oversize the hole due to other factors. and I would drill for the next size up pipe plug, install and lock in with thread locker, cut head off with a sawsall, and then drill and tap OEM hole size.
the cast drills and taps easy, AND if in a casting.. you are back to about the same strength and metal as the sourounding material. no heli coil to back out or loosen up.. etc. seals good too.. sometimes I've seen heli coils not seal well, for places that had fluid pressure behind them.
soundguy