I agree with what SWEET has in his reply. I have a 1950 3/4 ton that originally came with the 4.57:1 rear end. I found a '68 3/4 ton in a local salvage yard and took the "third member" out of it. There was immediate improved gas mileage and higher speeds. I also put some steel belted radials on the truck that are P265/75R16.
These two upgrades only cost me about $200! I found the tires at a swap meet on the last day when the seller was ready to get rid of them instead of haul them back home and the rear end was cheap because I was willing to crawl around under the truck to take it out.
Hope this helps.....
