Thanks, JMan! I looked at the block today, and there's the threaded hole right where you said it was. That answers two questions: where does the oil pressure switch go? and what's THAT hole for?

I noticed there's a similar hole on the passenger side also. I haven't inspected it closely to see if it's a blind hole or if it goes into something like an oil passage or water jacket. Do you know what that hole on the passenger side (circled in red) is for?



David