Drill and Tap block?

[saxart]

I'm in the process of adding Power Steering to a 350 SBC which has bosses that are not drilled to accept the power steering bracket that goes with the short water pump.



While I could just go with a long water pump, I'd really like to stick with the short water pump. I'm curious to hear from anyone who has had to drill and tap these holes in a block. I think I've learned that the hardware that holds the pump bracket to the engine are 3/8" diameter. Anybody know how deep the holes in these bosses need to be?

I'd hate to "drill through" a completely good engine block...

I'm familiar with drilling holes in cast iron as well as using taps, but just a little shy of messing up a good running engine. Any thoughts or experience you guys have is greatly appreciated.