My glimmer of hope has dwindled to a flicker. I put on a fresh filter, and refilled with 6qts of 10w30 full synthetic, and 1qt of MMO. Figured I'd drive it a little each day after work, and let the detergents do their thing for a couple hundred miles, or until the pressure no longer rose to an decent level at start up, whichever came 1st, then clean the screen again.
Went for a 5 mile drive between 25-45mph, and all was well until the last 1/4 mile or so when I got into it just a little, and brought the rpm's up to about 5k while accelerating. The pressure almost immediately dropped to 0psi. I put it in neutral while coasting, killed the engine, and restarted, and the pressure came back at 20psi. A few more blocks, right as I was turning into my drive, the pressure dropped again. Another shutdown/restart, and the pressure was back up again.
Does this sound like a definite pickup seal or relief valve, or is there a possibility that the sudden surge in rpms caused the pickup to suck up enough of the readily available gunk to re-clog the screen, and shutting it down for a second and restarting caused it to dislodge, and flow oil again?
I'll continue to drive it very close to home each day, making sure to allow it to get to operating temp since it needs cleaning out no matter what, but I'm assuming a tear down is imminent, based on the above condition. At least that's what I've read as far as the pressure drop, and sudden return with a quick shutdown/restart.