Thanks for the question Rod.
It wouldn't hurt to try changing the sending unit. That would be a cheap fix. The best way of course would be to check the oil pressure with a guage to get some true accurate readings hot. Most Chilton manuals will have oil pressure specs.
If the oil pressure drops considerably, more than likely the engine bearings are worn. As the engine warms up, everything expands and thus, clearances get bigger and pressure goes down.
Happy New Year