Some states have a rules like a vehicle must be at least 180 days old in order to be classified as used to avoid paying tax against it. It is longer in other states.
Research the state that you want to move to (on paper) for their rules on transfering a vehicle, titling, and registering it.
Your accountant may say that one of you with the smaller Oregon income tax exposure rent a private mailbox in OR, become an Oregon "
continuous traveler", and buy the truck. Remain an Oregon resident until the sales tax on the truck expires in the other state. Then move to the other state and tranfer the vehicle. At income tax time, you then should be able to file as part-time OR resident and prorate your income tax to the number of days you lived in OR for the year in which you moved to the other state.
The other spouse can move (on paper) to the other state as soon as it is feasible, and transfer any vehicles/trailers not impacted by a sales tax/use tax/property tax in that state.
The income tax and sales tax math has to work out in your favor. Your accountant should be able to advise you of your best options.