new rear end ratio for 1953 International R110 with a Silver Diamond 220

I have a pretty much stock 1953 International R110 with all original drive train. its got a silver diamond 220 with 4 on the floor and im getting a whole 55mph top speed so i'm wanting to change the rear end and put something that i can actually drive on the highway with. In the future i plan on putting a bigger engine and a 5 speed in it but for now just trying to figure out something that will get a better top speed without replacing the entire drive train. i believe that it currently has 4.10 gears in it right now.