[Walt Dupont--Me.]

You have done a good job checking every thing. My suggestion, I've done this many times on big truck engines. Remove the oil pan, hook up an oil pressure tank to the sender unit fitting hole, put a pan under the car to catch the oil, put pressure to the tank, look under the engine, see if you can see a lot of oil going past cam bearings, main bearings, or back of cam gear, ect. I have found the problem before. Walt