Outer Limits 4x4 Board

The oil pressure gauge on my 2H is going very erratic. It's an HJ47 on 350K (not original motor). When at constant revs (low or high, hot or cold), the oil pressure varies. It can be correct, then drops right off to VERY low, then climbs back up, in the space of about 10-15 seconds. Is this a relief valve problem, or more like a sender problem? Should I be worrying? At 2000 revs it's sitting on the lower operating region bar worst case, and mid-2/3 way up normally.

Are you reading this off the dash cluster, or have you tapped into an oil gallery somewhere?

Do not trust the dash gauge.

The FSM says that at idle the pressure should be 4.3psi, and at 3000rpm it should be 36-85psi.