If I can remember back to the last one I had in the shop, the factory manual (owner had it with the car) called for something like a straight 20W. With advances in oil I'd suggest a 10W30 modern blend (not synthetic). Expect it to make 15lbs of pressure (that is all a stock 6 cylinder made back then) and you'll be fine just as long as the engine is in good running order. I also suggest a compression check, you should be reading 110 at all 6 cylinders, or within 5-10% up or down for a normal "aged" original motor.


Hope you find this helpful.



Bill S.