Be cautious about simply adding the spacers on the rear axle in order to put two tires per side. This adds an imbalance to the carrier and is only meant as a cosmetic option. Therefore, if you intend to do some hauling with your new rig, you'll want to do an axle swap. The nice thing about a swap is that the frames are identical so it is a simple bolt-in operation. If you can find someone to swap axles with you, the most expensive part will be the fenders.