I purchased a Ford 1620 4WD about 20 years ago from a mowing company. It has Firestone Turf and Field tires on it that have served me well but now need to be replaced. The rear wheels are pretty much rusted out from calcium. I need to replace the rear wheels and tires and I wonder if it would be cost effective to change to Ag tires and wheels even if I have to replace the fronts as well. I priced the turf wheels from the dealer a few years ago and they seemed outrageous at the time (although I don't now recall the actual quote).