Longbox, do you know what OEM ratios were used? Are some more common than others or unique to particular years? It would be nice to find a factory setup that my son could use in his '66 C-10.
3.07, 3.73, and 4.11 are the listed options for the '66 1/2 ton. Just judging from the codes, seems that 3.73 is the most common, it has the most code listings, with 4.11 beinbg second. 3.07 only has 1 listing.
