Two scenarios for you.
1: Is the tank it is hitting steel? If so you're hitting a tank skid. The receiver goes on first then the tank skid fits over the receiver.
2: If it's plastic you must have an aftermarket receiver. Factory receivers do fit all year XJs, I have verified this on more than one occasion.
PS - If you do have the steel tank skid count yourself lucky, those are handy and not terribly common. If it's bothering you I'll take it :cheers: