You can shim the stock oil pump spring to raise the relief pressure. All you need is a bathroom scale, a drill press or other typr of press, a caliper, and a calculator:
Remove the spring.
Place it on the bathroom scale on the drill press table.
Measure the free length.
Apply varying loads by compressing the spring and reading the scale - lbs vs length.
This gives you the spring constant K.
Calculate the Area in square inches of the spring plunger by measuring its bore diameter.
For a given increase in pressure calculate the spring shim thickness needed: Pressure= K x (shim thickness) /Area.
