I bought a '48 Chevy pickup with a Buick 350 in it. The number 7 and 8 rod bearings were completely trashed. After debating whether to rebuild the Buick or swap in a Chevy, I decided to go with the non-bellybutton Buick. I had a local respected machine shop do all the machine work, including magnafluxing, which was my education in Buick head cracking. I installed a high volume oil pump and a booster plate from TA. I was disappointed to learn that the oil pressure, while adequate at startup, dropped alarmingly when the engine warmed up. The truck has a Classic Instruments quad gauge that measures pressure from 0 to 100 lbs, and it would barely register at light throttle cruise. I spoke with TA, and they said the high volume pump was a bad idea, and that the timing cover was the probable culprit. I replaced the timing cover with a brand new one, and swapped in a new "stock" oil pump. I also installed a mechanical pressure gauge directly on the block. I primed the new pump and saw a full 60 lbs with the electric drill. But when I drive it, the same problem remains. 50 or so lbs at startup, dropping to 7 -8 at idle, and less than 20 at a few thousand RPM when hot. I knew oiling systems were a problem with Buick engines, but I didn't anticipate this much trouble. Any suggestions?