adding front disc brake on a 1962 dodge dart?

For a '62 B-body, it should be the same as all the other '62-72 B-bodies and '70-4 E-bodies. they use the same control arms. The '73-6 A-body setup should fit right on it too even though the control arms are different. Just use your old control arms. Now, the power booster/master cylinder........I think I'd try to get one with a fairly small diameter for clearance around the firewall area. Maybe someone with that type car will know more about how much room you have there. It might be that any B-body booster assy. will work. Get the firewall plate and all the linkage for the pedal too.