I have a 440 stroker in a 70 cuda that the oil pressure fluctuates in,i have tried an adjustable oil pressure regulator, and then a new melling oil pump, and different weights of oil. there seams to be no ryme or reason to it. Somedays everything is fine ,other days its good and then drops to close to 0 after reving for a while, when I go back to idle the pressure will slowly climb back up and then go back down when the engine revs again. anyone have any ideas? It has a stock oil pan.