99 XJ Instrument Cluster Swap

Has anyone swapped a 1999 idiot light cluster with one including a tach? These XJ's are digital readout on the miles so I am not sure if the cluster itself keeps track of mileage or if it's somewhere in the computer. So will the new cluster show my real miles or the miles from the donor vehicle.
Any advice on this swap on a later model XJ would be appreciated including years that will work for a 99.

I pulled the cluster completely out of my 97(w/ digital) and took it apart to install some fancy white gauges. When I plugged the cluster in the Odometer still read true, so I presume the info is stored in the computer.
Barger

My brother recently purchasd a 99 SE model, one with the idiot lights and nothing else.. He went to the junk yard and pulled a 98 cluster with all the guages. He put the new gauge cluster in and it came up as 121k, his old cluster has 36700. Its being stored in the cluster itself.

My question is does anyone have any information on how to transfer the old mileage to the new Cluster?

He has his old cluter, the one with idiot lights. We took them both apart and swapped out the little digital LED lights, it was a seprate unit on the dash. No luck still same mileage which is making me think its one of those rom chips on the circuit board.

Anyone have any luck or information on which chip? Or have then swapped it?

I have a 98 XJ and swapped in the cluster from a 97. My odometer read 30K more than what I had. What you need to do is take the new instrument cluster to a speedometer shop that can calibrate the newew style instrument clusters like we have in our 97+ XJs. The ECM and the instrument cluster have their own memories and interface thru the two instrument cluster docking ports that are fastened to the dash panel.
The ECM and sensors take care of sending the signals to the gauges on the new instrument cluster.

Stealerships

I did a swap on my 97, and "lost" about 40k of miles. I was prepared for the opposite, however, and talked to my local stealership. SOME dealerships can alter the codes, reverting the miles, but I seem to recall you need to bring the "old" guage cluster for "proof" or reference.
Even with the altered miles, it was the best improvement I've done, for real cheap, also.
Man, the clusters suck! Chrysler is SO CHEAP! Every XJ should have the full gages. Period.