Oil pump pressure relief valve was the case in my 1967' 327 Corvette...
Oil pressure was great except under braking, accelerating or had cornering.
Pulled the pan and found a "press-fit plug" that eventually I realized had popped out of the side of the
oil pump body, probably on initial start up. Found the plug first time I pulled the oilpan...put it on the bench as a monument to careless junk in the engine...pulled the pan 2 more times, adjusting the pickup to no avail...finally pulled the pump and the pressure relief plug was out...
Simply using a cold chisel to stake the plug would have saved the crank.
I have no idea what the valve assembly in a filter or Ford oil pump looklike, but if there are ANY drops in oil pressure, suspect the pump.
Pete