What rpm are you seeing 30# if it is at 2000+ then it is low. Lots of things will cause low high end oil pressures.
If you have a mech gauge, get a second opinion (another gauge and stick it in one of the 1/8 npt ports on the block right above the pan rail).
Sorry if you already posted this but who rebuilt the engine? What was done?
Remove the oil filter and cut the top off of it. Inspect the can and element for signs of bearing failure. This would be a lot of non- magnetic silver/copper particles. Non of these?
A few causes for low oil pressure are.
Bearing clearances larger then spec, main, rod, cam.
Oil pump gear to gear clearances big.
Oil pump gear to housing clearances big.
Oil pump gear to cover end clearances big.
Oil pump relief valve not set up correctly.
Oil pickup tube to pump oring incorrectly sized/installed.
Poor oil viscosity (40 wt on the big number will help)
poor oil filter flow some good makers of filters have been mentioned.
Low oil level.
Internal oil gallery plugs missing.