Check your oil level - sounds like it may be low. Oil pressure will not drop at high revs unless there is surge or low oil.
Or... being an older engine with lose tolerances a lower viscosity oil may show a drop in oil pressure when hot or revved, you may need to increase the oil viscosity to compensate for the age of the engine..
My Falcon family heritage: XY V8 Falcon 500, XYGT, XBGT, XC 351 GS, XD 4.1 Spack, EF wagon, AU Wagon, AU2 Wagon, AU2 XR8, BA XR8, BF XR8, FG XR6, Sprint 8. AU3 XLS Marlin Ute, FG2 Ute, 996.2 Carrera, MY24 Raptor.
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