You mention "new pump". Is this a demand pump or a pressure pump? I suspect your '66 came originally with a pressure pump, but they frequently are replaced with a demand type due to the very high cost of new pressure pumps.
If a demand pump, you should have an inline filter just upstream from the pump. Typically, they have a transparent plastic cover which is held on by a screw or bolt. You remove the cover and the screen is accessible. Be very, very careful to reseat the cover when reinstalling as the pump will suck air given even the smallest oportunity.
If a pressure pump, I can't help. Someone on the forum can, I am sure.