The oil pressure gauge reading doesn’t really have any bearing on this. First question I’d ask is, are the baffles still in place in the current valve covers. Sometimes they’re removed for clearance when using roller rockers with the originals. If that’s been done then using spacers under the covers and replaced baffles should fix it.

Also, are you running a hose from the oil fill to the air filter as original?? If not then crankcase pressure coming up through the oil drain holes in the heads could be picking up oil mist as it exits and since there’s no draw to the intake it just dribbles down the filler.

How did you break it in?? Could be excess pressure for awhile as the rings seat and it goes away on it’s own after a few runs. Or could be that the builder didn’t do everything he should and they’re not seating, or perhaps even damaged causing excess internal pressure.

Just some things to check and think about. Could be any one of these or something else, but at least it should give you a starting point.