Sometimes if you want a whole different truck, you should buy a different truck. Sometimes you can modify it without a lot of money. A V8 will drop in fine and so will an auto. You have a torsion bar suspension, some folks don't like those. 63 and up has coil. Disc brakes are $125 for the mounting brackets and bearings, you buy the rotors and calipers. $650 complete and then you will want power brakes to go with the disc and the saga begins. You do not need a different frame. It will stop, a safe driver, with drum brakes even with a V8. V8's may weigh less than some 6's and the speed is there for both.
