As you look at the engine it is to the drivers side about 4-6 inches from the distributor. It comes out of the block with a 90 degree fitting and the oil pressure sensor screws into the 90 degree fitting. Also, I don't recall exactly how it goes as it has been quite some time but the early GMT400's had an oil sensor or switch that is by the oil filter.
Ok I did see something resembling a 90 degree fitting. But I was told to look on the passenger side so I didn't think that was it. I'll go back out tomorrow and look a bit closer. I have a bad shoulder, neck, and back so I can only look for a few minutes at a time. The 90 degree fitting that I saw appeared to be chrome or a silver color and was under the dist.