During my posting at Ford Motor Company's Cleveland Engine Plant #2, I had the opportunity to meet one of Ford's lubrication specialists and asked him the same question about oils. He recommended Quaker State or Shell Rotella type oils. These still have good trace elements of Zinc which the older engines need as part of lubrication. While straight weight oil (consult the shop manual for grades, based on temperature) was originally specified, 10W-30 (SAE standard) will work ok.
Some will say non detergent oils should be used rather than degergent, but he didn't think it would make a difference in the long run. The detergent oils will open up areas that may have been plugged over the years, especially if prior owner(s) used oil with a bit of parrifin in them.
This is only an opinion. I would recommend you contact the customer service departments of the companies mentioned (both are units of Royal Dutch Shell) for better info and something "official".
