OEM Gauge Update - how to set the ODO

[JeepNmpg2]

OK, my stock Jeep Cherokee SE cluster came with a speedo and HUGE fuel gauge + four idiot lights. I just aquired a cluster from same year but with all of the normal gauges (tach, volt, oil pres, temp, fuel). From everywhere I've looked, everyone says it's a direct swap, but no one says how to modify the milleage on the ODO. Not that I don't mind losing about 16,000 off of my vehicle, but I need to be as legal as possible with this. Any ideas for how to modify the mileage?