Robbie,
The standard gear ratio for the 1/2 ton Task Force trucks (55-59) was a 3:90 ratio, unless it came with overdrive in which case it would have a 4:11.
I am fairly sure that the early 60's trucks followed that same pattern. I guess it depends on how much running you plan to do at freeway speeds what ratio you would be happy with. There were other higher ratios available which would make for better cruising speeds. A 235 is wound up fairly tight at 60 with a 3:90 gear. I put overdrives in everything so I don't have any issues with ratios.
Fred
