Any oil pressure at all means the engine is getting more oil than it needs. Pressure builds up because the pump is supplying more oil than can be leaked away from the bearings, etc. while the engine is running. The only problem is that the pressure port on a small block Chevy is closer to the pump than to the end of the oil circuit. The front two connecting rods, #1 on the driver's side, and #2 on the passenger's side are the last items in the pressurized oil system to get lubricated. If you're only getting 5-10 PSI back at the pressure port, there's no way of telling how much oil pressure, if any, those front rods are getting. When you've got the pan off, drop those front two rod caps and inspect the bearings for scoring or scuff wear. Chances are you're OK, but it only takes a few minutes to check. It would be pretty easy to use Plastigauge on all the bearings, rods and mains, while you're in there. An engine with that kind of oil pressure after a rebuild would never have left my shop until the cause of the problem was discovered!
BTW, the high volume oil pump part number is a Melling M55HV. It has slightly longer gears and pumps more volume than their OEM equivalent M55 pump. It's usually used on race engines with bigger than standard bearing clearances to reduce rotating friction. That causes low pressure at idle and low speed due to more leakdown at each bearing.
Jerry
