I found ATF seemed to give a quick throttle response. I've heard 3 in oil is 20 SAE and should be ideal.What CJD said. The only thing that didn't work was WD40. ATF, 20w, 30w, 10w-30, 10w-40, 5w-30 any medium grade oil/lubricant will work fine. I have tried many different, unless you go way too thick or way too thin you won't notice a difference.
I just realized that whale oil was still available when these cars were built. Wonder if that would have been a recommendation if we had internet in the 60's?
Sorry...been cooped up too long.