59 AB in 35 ford maxing out oil pressure gauge

[bosscat28]

It reads 0 with the key off
5 lbs with the key on not running
maxs out past 50 while running at an idle
I don't know if it has a pressure relief in the pump.
It's still 6V pos ground

I bought the truck last year. It didn't have an oil pressure gauge or sender.
I bought a dual gauge set up oil pressure - fuel gauge.
Got a 50 lb sender & just hooked it up today.