Early to mid fifties to 1996 full size Ford truck (1/2ton or Bronco) will have a 5 on 5.5" bolt pattern, 97 and up have a METRIC pattern and will not fit the earlier trucks. A 31/2 to 3 3/4" back space is probably what you will want to buy, anything more than that (4 7/16, 4 3/4 will put your tires completely under your truck, and you may find that they hit the frame and radius arm when turning.
(Be aware of the mid-nineties odd ball 7700lb gvw half ton that had the 7 bolt wheels.)
For a 10.5 or 11.5 tire you should try to find an 8 or 9" wide wheel. For a 12.5" wide tire use anything from 8-10" wide wheels.