Keep in mind whatever wheels you add will lower the distance from the bottom of your coach by the dimensions of the wheels. If the wheels are 4 inches ... you'll be 4 inches closer to the ground. That means you'll be hitting a lot of things you never hit before.
Many add a 1/4 - 3/8 steel skid plate about the size of your hand to the area that drags. That limits dimensional issues and still saves the hitch or whatever is dragging. On one coach I had to have two skid plates welded to the hitch at both corners. Yeah they drag, but so will wheels. The plus side is no damage is being done to the coach if they hit, not any closer to the ground, and no wheels to replace that get torn off (and sooner or later they will).