when reving the engine is there any fluctuation in the
oil pressure. if so that would indicate the pan running dry.
what
oil pressure i like at idle would depend on the crank rod journal size you have.
factory ford rod size= 45 psi min
chev journal=30-35 min
i would start by trying a thicker
oil but i don't think it is the root of the pressure problem. the rockers would be my first place to check too.