You should be able to find a used OEM carrier in excellent condition for next to nothing. Snubbers (tailgate bump stops) are what your spare tire will be up against when mounted. It helps to keep the tire from moving (vibrating) when the Jeep is underway. Without them you run the risk of cracking the carrier itself or worse.
If you are missing them then you can either get them (OEM) at the dealer or buy these
. For the Daystar ones you just cut them (very easy) to fit. You also want the tire when mounted to be up against them tight. They should actual deform (bend) a small amount.
The tailgate will have two small holes for the bump stops. All you do is just push them in.