That's a bummer. It would have to be the B&M setup then for the pan plug. Of course, once you get to the point of buying a tap, or welding fittings on pans, whatever, it's probably the cost of just buying an aftermarket sender.

Any chance GM (or anyone) went with smaller than 3/8" coolant stuff?

IIRC, the oil pressure switch/sender that screwed into the block was 1/8" or 1/4" (MOST oil holes in the block were 1/8) finding a smaller stock sensor could be another option as well.

One above the oil filter, if tapped, was typically 1/4"? I suppose you could "upsize" one of the block fittings, but not sure how accurate the oil temp would be compared to pan. Never have seen oil temp at various locations in the block covered.

Still have the aftermarket sender option, but the three wire stock one is attractive.