I replaced my cluster unit, but this cluster does not have the same km-reading (+/- 135000) difference. How do I adjust/reset it to correspond with the logbook?
You can't. Well actually you can. You can remove the EPROM chip from the cluster and make it virgin. Then code it to match the existing miles.
My recomandation would be to find a cluster to has about the same miles as your. Either way you should mark you car miles expet or not acual miles when you sell it depending on your state laws.