360 engine sudden drop of oil pressure while cruising at 3200 rpm

Why not try to spin the oil pump with a priming shaft?

remove the distributor and distributor drive gear and try to spin the pump with a priming shaft on a drill and see if you can develop pressure...

Check the bottom of the distributor drive gear for any signs of the hex getting chewed up, if not, then check the oil pump and pick-up tube. Is the pick-up tube in tact? Is the oil pump seating properly on the main bearing cap, or is there a gap?