The best solution is to get a rear end from a later model truck. Assuming the rear cover has 10 bolts holding it on, the gear in your truck are about 5.14 or 4.57, I'm not sure on the specific ratios for the 62. Your only upgrade using your differential is the pumpkin swap from a 64-72 3/4 ton, 4.10 gears which are getting a little bit scarce. I would start by visiting a local salvage yard, if you have one that has some older trucks. See if they have anything to offer.
