My Receiver Hitch Won't Fit...

I purchased an older Reese Brand receiver hitch that came off an older style XJ. As I was attempting to install it on my '98 XJ, I realized that it wouldn't go on because the crossbar interfered with the fuel tank. I know that the pre '97's had a steel fuel tank and the post '97 have plastic tanks, but I assumed they would be the same size. Anyone have any experience with this? I'm wondering if I am out of luck and just need to buy a different hitch, or if there is something simple that I am overlooking.
Thanks-