So...I ended up buying a steering column for the XJ from a junkyard (the bearings in the old one probably just need to be replaced, but I was fed up with it). After driving about 5 hours to pick it up, I got it in and drove to the gas station to fill up the tank. I had noticed the engine had been running roughly, and it only got worse on the way home from the gas station. It turned into what felt like the engine was swinging free, and either I had forgotten to reattach the nuts to the crossmember and the tranny had broken loose, so to speak, or I had a broken motor mount. So when I got home, I climbed under, the nuts were there. I checked under the hood, and voila - passenger side motor mount is split in half.
My question is this: Should I replace both mounts at the same time? and also, should I upgrade to heavier duty mounts?