Yes just change Rhydon in Rhyperior, the stat change is done alone
the problem is that pkhex will put on Rhyperior a flag on the, because it has not been exchanged, if you need a other OT for "Lastest (not OT) Handler " by pkhex take OT : Yggorfillia / girl
or you pass the wc8 of your Rhydon...