I did pretty much the same swap on a 64 Belvedere wagon. I used A-body spindles with the calipers front mounted, A-body proportioning valve,11.75 rotors with pin type caliper adapters and calipers and hoses from a 70 Roadrunner.I used a NEW master cylinder for a 70 Roadrunner with power disc brakes. I cut 2 small notches in the bottom of my k frame, and used a sway bar from a 70 Roadrunner...and also the lower control arms from a 70 Roadrunner. Can you tell I had a 70 Roadrunner parts car? My wagon was a factory power drum brake car, is why I went with the power master cylinder, and the Roadrunner master cyl bolted right up. That behemouth would stop on a dime and give you nine cents change after the swap! Good luck.