One thing for sure - 5 psi at road speed is not enough . . . so until you fix the issue, I'd not be doing that.
As noted, I would pull the pan first and check/clean it all out . . . and probably think about a new (later) oil pump. You can put an 8BA pump in it with the necessary pickup for the early pan. You can buy the pickup at Speedway - which beats the heck out of having to cut, splice, weld up the later pickup for usage in the early motor.
Pickup: (without the screen - they can supply with the screen).
https://www.speedwaymotors.com/Speed...Tube,4289.html