Danny:
The factory transmission options for the '64-'66 Chevy Series C10, C20 & C30 and K10 & K20 trucks were 3-speed (manual, column shift), 3-speed w/overdrive (manual, column shift), 3-speed wide ratio (manual, column shift), 4-speed (manual, floor shift, SM420/SM465), Powerglide (two speed automatic) and Turbo-Hydramatic (three speed automatic). This information is per the General Motors Silver Book. I don't believe there was a 5-speed w/overdrive tranny option available. I hope this information is helpful.
Tony
