rockwell axle and tractor tires

I have 2.5 ton rockwell axles on my mud truck with 42" super swapers but I really want to put tractor tires on it but don't have the first clue as to how to get them to bolt on the axles. Do I need a special type of wheel or do I have to do some of my own mods to get them to bolt on? I don't want the big tractor tires but the smaller front ones that are on the 4wd assist tractors. If anyone can help me either how to get them to bolt on or where I can find a set of 4 would be great.  I also need some ideas on how to get the breaks for the axles?  Or if anyone has good ideas on how to make my truck a beast, right now it has a 502 caddy motor I would like to put a cummins in it maybe.  Thanks.