Oil pressure switch

There are usually two places you can pick up oil pressure without major (or any) surgery. One is the obvious location at the rear of the oil pump where the pressure sender is usually screwed in. The other is at the rear of the main oil galley on the distributor side of the block—there's usually a pipe plug, same 3/8" NPT thread as the sender port in the oil pump. The factory put the pressure sender there in some '63-'64 motors (with a pipe plug in the oil pump), but on very hard braking sometimes this location would momentarily run low on oil, making the oil pressure warning light flicker and frightening Mr. and Mrs. Carbuyer, so they moved the sender back to the pump and issued a TSB for dealers to do the same for whoever came in with that complaint on one of those cars.