I don't think there are any current 747-8F white tails - Air Bridge took them after the original buyers backed out (presumably at really good prices). Intercontinentals are a different story - there are several white tails for operators who went belly up before taking delivery. A few are parked in the desert, at least one is still parked at Paine but will be heading to storage before the end of the year.
There is minimal 'customization' of freighters - so transferring buyers is not a big deal (assuming you can find a buyer) - passenger models not so much...