First it won't be cheap....you need to get rid of the 15 inch tires and wheels. I can't believe any manufacture would install 15 inch tires on a 5th wheel that size. To me that is negligence... Good news is other people have done it and with a little luck you will have enough room between axles that you may just have to buy the rims. But you will have a had time finding 15 in. LT tires. But once you get 16 in tires on get LT's and but heaven forbid do not get Marathons. Surprise, surprise the newer Cruisers have 16 in. wheels on them.