This comes up from time to time. This is cut from a response a while back from Aaron Storms on the the Colorado XJ group: "Unfortunately this is actually pretty common, especially on older xj's. If I have to cut the big hanger bolt off to get the leaf springs out, I then flip up the back seat, peel up the carpet and plastic moisture barrier, then determine where the "frame" indentation is and cut a 3-sided door or access hole inside the frame area. This way you can remove what's left of the bolt end and nut, then have a place to get a wrench on the new nylon locking nut you're going to put on the end of that big 6" bolt you're going to buy to replace the old bolt you just cut off...
I usually use axle grease on the bolt shaft where it slides inside of your new leaf eye. When it's all tightened down good, bend your access door back down, replace the plastic and carpet, fold seat down and all is well...and you've managed to keep most of the moisture and junk out of your frame rail without compromising the strength of the "frame." The hardest part was to figure out what was the best solution all these years!"
