That is an Autolite 1100 1bbl and you should be able to swap in the rearend from any Ford pickup up to '79. Or you could just swap out the center section. Your pickup and most (all?) Ford pickups up to about '80 and a lot of full sized cars, used the venerable for 9" The only thing you have to make sure of is the axle spline count. Otherwise find a gearing that you like, unbolt your current one, bolt in better, more highway friendly gears.
-ron