Hello my name is Garrett and I am a farmer in Nebraska. I just bought a 4850 2wd. It only came with 2 rear tires and they are 20.8-42. I farm 30 inch rows and would like 18.4-42 and duals. I would like to know if they are the same height as the 20.8's? what kind of price they would run for rim and all? and where I could find some used ones Farley cheap? All suggestions are welcome and would be much appreciated.