Well, considering that I have a '97 and a '01 and have removed & installed hitches on these and earlier models, I'm fairly sure I know what I'm talking about. There is a rubber block style mount at the cross member for all years, but back by the fuel tank (where one would tend to experience hitch interference) the '97 has a similar rubber block style mount with a rigid rod welded to the tailpipe (as I stated earlier.) Later and earlier years have the floppy (for lack of a better word) hanger that gets u-bolted to the tailpipe.
Regardless, the hanger should have been held to the frame with 2 bolts that thread into the nutrail... are these the ones that won't come out? Or does yours have studs that won't come out after removing the nuts and hanger? If that is the case, you could thread a nut onto the stud, weld it in place, and then try turning them out with a socket wrench. Or, if you don't have a welder, you could thread two nuts onto the studs and jam them together, turning the stud out with an open ended wrench.
If you have bolts that won't come out, you could cut the heads off, remove the nut rail from the frame and then drill out the remaining bolt and chase the threads in the nut rail. Far less labor would be to replace the passenger side nut rail entirely.