I've had a lot of success with oil pan gaskets by throwing the cork gasket away and just useing the black or blue RTV, apply a liberal coating, circle the bolt holes and bolt it into place. Let it cure and it won't leak. Cork gaskets are famous for scooting out of the way as you tighten them up and adding RTV to that equation just makes it worse. Using both seems redundant to me so I just use RTV, and on 6 restos its still holding up. These old oil pans are really hard to get flat enough, especially with the rib in the center which is supposed to be the pressure point for the cork gasket. My 2cents.