[Captainfab]

The C20 and C30 control arms use the steel bushings just like the '63-'72 C10's did. The main issue with using the C20 or C30 control arms, is the lower ball joints are bigger than the C10's. There's really nothing to gain by swapping your '64's control arms for the C20 or C30 arms unless you want to use the '88-'98 LD C2500 parts. This would give you 6 lug front discs

If you're having trouble locating the '73-'87 C10 control arms, I would just keep your original arms. Then just buy your drop spindles, and which ever rotors you decide on.

The steering boxes are the same whether from a C10,C20 or C30. However I don't know if the steering linkage will be the same. It is doubtful. The C20 or C30 sway bars will work on your truck. Often times you will find the larger 1- 3/16" bar.