The actual oil pressure sender for gauges should be on the driver's side of the block, just above the oil filter. I saw it there on the 82 Monte that donated my gauge package. To get at it you'll need to remove the driver's front wheel. You'll see a a threaded plug in the block where it should go.
Yup, that's it, Ernie. Here is what it looks like on my 229 V6 (stock without gauges and before the planned upgrade.)
Notice the hole is there and set to accept the sender for the gauge, just screw in fittings. I'm all set to go for my gauge package, just need to start plugging things in... with the exception of having a stock GM tach for a V6. I will do it all with a V8 tach and swap when I get a different tach. Can anyone help source a V6 tach?
I totally get what you are saying, Ernie. So many years to take into consideration. I thought I could add to the possibilities and help future searchers of this thread.