Break In Disaster????????

I would check for burs or nicks in the washer and shaft. if it's good and still leaks, buy some brass shim stock, cut to fit and install. if there is no crack in the shaft at the bolt hole, problem solved.

The oil pressure is high BUT, my last eng. hand 80 at idle cold and around 65 when hot. rev it up when eng was hot and it would still go up past 80(my gauge only when to 80) ran that way for years(was running 20w50 oil) Ended up going to a synthetic 0w40

my 340 ran for 10 years on that high oil pressure, before i when to the thinner oil.

Personally i thing you ended up with a High volume pump, for the price of a stock one. that's what i had.

After you get it broke in, run a thinner eng oil and see what it does. BEFORE, you go pulling The oil pan.