12.50s work fine on 8" rims, stock rims are 6" and 7". Some folks run 12.50s on 7" rims, but a better option is a 33x10.50 tire. Fits the stock rims and is a little easier to fit under the truck:

33x9.50 and 33x10.50 on 6" rims:

[Linked Image]

http://www.4crawler.com/4x4/BFG_AT_KO.shtml