Many would say that these numbers aren't bad for an engine with a lot of miles on it. If you want to verify your oil pressure install a mechanical oil pressure gauged (temporary or permanently) to double check what the pressure is.
The pressure relief spring should not change as the engine warms up. The oil viscosity thins out as it gets hotter and with increased clearance in the bearings the pressure decreases.
What viscosity oil are you running? How many miles are on the engine?
If you want to read one (of numerus) thread on this topic, this is one currently up:
https://www.fordbarn.com/forum/showthread.php?t=283042