I would go enjoy the trip with the temporary tag. It will be perfectly legal for all but the last 4 days of your trip. It is very unlikely that you will be stopped during those final days. IF you are, just explain the situation and hope for an understanding officer. Having some of your supporting documentation on hand would likely help.
I would NOT place a plate on the vehicle that does not belong. This is being deceptive and if caught you will not likely receive any sympathy whatsoever.
'04 GMC Sierra 2500HD, CCSB, D/A, MaxBrake, B&W Companion, Retrax Pro, AR Power Steps
2013 Rockwood 8289WS w/Diamond pkg
1969 Camaro RS/SS Convertible
Dad's old 1968 Empi Imp (recently recovered from under 21 years worth of boxes/dust)