Just change oil to a thicker grade oil next time. In '65 Pontiac shop manuals said anything above 3 psi was enough oil pressure, in fact the light on the dash came on at 3 or less PSI. I would think for a older engine, your pressure is close enough. Even new they didn't have much more then that. Lucas oil products will thinken the oil and help the engine at start ups, its one of the few oil additives that really works.
Joe
