Planning a 440+6 tow vehicle, need a plan

I would scratch the idea of using a car. mid size to full size wagon, yes.. I suggest an aluminum like airstream, you said you want vintage, I remember all the Yanks hauling *** down I 75 down Ga in the 60's... ha
better choice is 3/4 ton pickup. wish I had a dollar every time I have seen some r etired guy roll his rv trailer going down the interstate pulling the big sucker with a 1/2 t or suv! BUT the salesmans looked it up, and the factory said it is rated to pull his big rv! ha yea.
440 in our rig and pull a trailer? 5 mpg sound good? IMO