87K is a little high for an 04, but like stevens said; you can put 250K to 300K on a well-maintained 4.0.. I put 150K on my 89 YJ w/ a 4.2. She was a runner and I beat the tar out of that rig..
I guess I would say that is a good deal considering I paid $12.5K last summer for a 2000 sport lifted 4", D44, warn8274 w/ 69,800 miles, and dual tops.. She was babied and spent most of her time garaged... I have almost $20K into her today...
Definitely think about what you are planning on doing with it because those good upgrades aren't cheap and at last check, UNICEF wasn't in the "Jeep ugrades market."
OH! X2 on what stevens said about the D35.. Use that as leverage while working the deal my friend.. if the guy isn't a real jeep guy; he probably won't know that D44 rear ends were only offered as an option in Sports, Saharas, and standard in Rubicon..
Have fun and best of luck to you!