You need the Selecter: http://www.geocities.com/braunovi/Selecter/SelecterD1980TooMuchP.htm

Pressure is usually caused by something clogging the oil path, as in sludge. I would verify all passages are clear. Chances are your bearings are oil starved, so I wouldn't drive it until it's figured out.

The positive displacement pump is not likely to fail and generate a higher pressure.