The Mustang rotor swap involves a little creativity and dinking around, but since you already have a good brake setup on the car it may be the most cost/time efficient solution.
You’ll need, new or new to you:
- upper control arms to accept the larger ball joints
- spindles
- caliper brackets
- calipers with hold down hardware
- 73 and up disc brake proportioning valve if you don’t have a pro valve already for Kelsey
- pads
- rotors
- soft brake lines
- lower ball joints
Some people retain their 67-72 upper control arms and put a sleeve over the ball joint stud (most call these ball joint adapters) but I personally would not go that route.
For the mustang rotors you will need a sleeve on the spindle where the seal rides. Due to the seal being a larger diameter. Also the inner bearing is a different number for the larger inside diameter. Otherwise it is a direct bolt on.
Using the mustang rotors is a much better choice. Why? because if you use 73 and up brakes you will have fenter to tire clearance with 6 inch wheels. The 73 brakes move the wheel out 3/8 to 1/2 inch and then add the extra 1/2 inch for the 6 inch wheel. Unless your running front runners tire size will be an issue.
One other plus with the 4 piston calipers is that they free wheel when released. The single pistons always have a drag and run hot. They also create a lot of brake dust and the whole assembly is much heavier.
All good aftermarket brakes are no less then 4 piston and at time 6.