Normal running oil pressures for a Northstar should be HOT: 20 psi at idle, 40 -45 psi cruise (2000 rpm +). Cold, high idle, maybe 60 for a while.
Entirely possible someone stacked one or two washers under the oil pressure relief bypass spring when they built the engine. BUT, that involves quite a bit of disassembly to check. Use a mechanical gauge to check first.
Good oil volume and flow is critical, not so much high pressure. GM likes 40 -45 psi hot, Ford usually likes 45 - 55 psi.
What weight oil are you running ???? 10W-30 should be plenty.