I have never had trouble finding wheels, aftermarket or original, to fit the six lug configuration on the '64-'66 Chevy trucks. I put a brand new set from an '86 Chevy K1500 on my '66 Chevy C10, back in 1986. I have a 2000 Z-71 Tahoe with six lug wheels manufactured by American Racing that will bolt on any of my '64-'66 C10/K10 trucks. The rotors and calipers for six lug disk brakes are readily available over the counter from any local parts supply house.
I scratch my head every time someone is told a disk brake conversion, also means changing from 6 lug to five lug, in order to find correct fitting wheels and disk brake parts. That notion is a myth. Each of my '64-'66 Chevy trucks have a different style of wheels from different manufacturers.
If you want disk brakes, you have many choices of wheel styles, sizes and manufacturers, as well as readily available brake parts, over the counter. Good luck with your conversion.
Tony
