I do know that 71-72 spindles will fit a 67 and most likely a 64. I believe both used the same front end. Anything after that would be questionable but you may be able to swap the whole crossmembe. I did six bolt disks on my 67 by using parts from a 71-72. You really need more then just the spindles to do the job correctly. I kept the pattern six bolt by getting aftermarket hub/rotors that were drilled for six. They are available but pricey.

Stock wheels may or may not clear the rotors. Mine didn't. I'm using stock six lug wheels from four wheel drive trucks with disks from the 70's and possibly 80's.