easyrider,the 91 3.5 dosent have any access to the oil pump except removing the oil pan and that is something that should be completed on the 603.970 engine in my opinion.if you want to read there is a lot of earlier comments about these engines.i can tell you for sure that these engines are a ticking time bomb,bolts come loose from the oil baffel plates and get into the oil pump and it will destroy the engine.it is possible that the washers have already reached your oil pump screen and have created restriction,but i cant see the pump going to zero with just a couple washers there now.
one suggestion for low oil pressure would be a leaking oil sensor which is located at the oil filter housing,but you should be seeing the lost oil on the ground as it leaks from the belly pan. this should not cause any additional noise fron the head unless it is a major leak and you should have seen the oil down on the dipstick after a 350 mile trip.
larry perkins
72 old cars