I am doubtful on the pickup being the source of low pressure - the engine would starve and seize if there wasn't enough oil flowing.
Pressure must first exist - which is not the case if the pump innards are worn - easy rebuild/replace with the engine out and the pan off. Once the pump is making pressure then the reading on the gauge is all about clearances: mains, rods and to tlowes point the cam bearings. Many rebuilds ignore the cam bearings because of the tooling needed to replace them - moreover the shop manuals will lead you to believe that wear in this area is unusual: "Replacement of these bearings is seldom necessary" 1949 Chevy Shop Manual section 6.
I would plastic gauge the rods and mains while the engine is out. If the clearances are excessive on the rods or the mains you could replace the bearing shells. The compression test results are passing the 10% variance rule - all six holes are within 8 psi or less which is just shy of 7%. No reason to touch those.
Not sure about the later sixes but in the stovebolts the dealership service techs would perform an in the car replacement of just the lower bearing shells on the mains with .002 under-size in order to correct low oil pressure (that is once all of the 'select fit' shims had been removed - but clearances were still excessive). The lower shells do all the work in an I6.
Not sure if anyone has done this on a 250.
