Between the 1959 and the 1961 Fastwin (18hp): I know the needle valves are different lengths, due to hood & adjustment linkage differences.
Too tired to go down to the garage to see if the ’59 uses the same (troublesome) plastic "detent" for the choke that the ’61 uses…..
I’ve never had a complete parts list for the 1959 (or the 1960, which I imagine would be similar, since they had the same shape hood).