Rebuild turned bad

We put new main and rod bearing in my 390 stroker and new rings and new Melling high volume oil pump and pick up tube old bearings didn't look bad at all when we got it back in the car and started it up it went to 70 psi oil pressure the when warm and we reved up rpm it went to 100 another buddy had the same thing happen before and when he went to the burnout box so he had a new pump he had for a while we dropped the pan and changed the pump which was the same we had on the car fired the car back up this tine it went over 100 and pegged the oik gauge we even changed the gauge after that sane results any ideas what caused this .