69 dart disc brakes

No, large bolt pattern, disc brake rotors from the A, B, E, body or F, M, J, body Do Not Work, Fit, on a 65-72 Kelsey Hayes, 4 piston caliper, disc brake spindle.
The "shaft" on the spindle is too small for that.
There is a vendor that machines early Mustang rotors to work with an early KH spindle, to go to big bolt pattern.
That's the only way it will work.
Lower control arm stays the same, doesn't have to be changed.
Just the lower ball joint to 73-76 A body ones, when changing the spindles.