Switching frames would not be fast, easy, or cheap.... Lots of companies making Mustang II style front suspension kits for the front.... Fits the stock frame very nicely and gives you the disc brakes and good steering. Leaf springs would be fine in the rear, if you have a 12 bolt to swap in the car that would be the way to go especially if it would happen to be the correct width! Some good shocks and ladder bars with a housing floater would finish out the rear just fine, or toss the leaf springs and go with coilovers and a 4 link. None of this is quick, easy, or cheap either....