Going back to the oil for a minute, I think the thing is that in 1956, a Fastwin had plain bearings on the small end of the connecting rod, like the infamous tens; so you’d want 16:1 in 1956 and before. In 1957 and up, they had a roller bearing, thus you could use 24:1. I am just going on memory of taking a number of these apart; so correct me if I am wrong on that.
(For the 7.5, there is no question or debate: 16:1.)
Long live American manufacturing!
