well dunno if you'll find em on tractors or not they usually have pretty big rims . . .the 20.5x25's are on front end loaders and stuff and are 58's . . the 67's come off logging equipment and not sure what 66's come off of . . . found a set of 66x43x26's on ebay on 12 lug rims but they wanted like 2500 each lol