This is just for conversation and nothing more.

We built a chevy 454 years ago. Rods at .0025 Mains at .0028.

Had an Melling HV pump in it on the stand and started playing with the pressure relief spring in the pump. We would spin the pump and watch the pressure readings after adding shims. Kept adding shims pressure went up and up.

We wanted to see where it would just give up and produce no higher pressure. We were shocked to see over 250 psi. This is with a spacer we finally installed to limit the relief to just lift off the seat in the pump and no more. This was on the stand now, not running but we would rotate the crank.

My point is the pump is capable of producing high pressure.

You never mentioned what the oil pressure in yours was on the first fire up.

Good luck my friend, I hope you get her figured out!