The cheapest way to go would probably be to get the parts from a '73-79. They also make kits for a disc brake swap but they are outrageously expensive. Or you could find a bump with disc brakes I believe in '71 they made them an option (not 100% sure what year), I will send you a few links in a min. or two once I dig them up explaining the disc brake swap from a '73-79 onto one of our wonderful bumps.