Re: Flag on vehicle
Greetings, Pohenn -- welcome!
As you pointed out, the only guidance in the flag code is the part about putting the flag on the right front fender. This was obviously based on the practice used on official and diplomatic vehicles. A personal or organizational flag goes on the left front fender of such vehicles.
In your case, I think you can basically do what you want. However, the basic principles should still apply: the US flag should be to the right of other flags (as viewed when facing forward), and the other flags should not be higher than the US flag. If you had one pole on each side of the roll bar, with the US flag on the passenger's side and the Gadsden on the drivers's side, that would seem to be fine.
Is there any chance that you might take a photo of your truck with the flags mounted, and post it here?
Best regards,
Peter Ansoff
"We live by symbols, and what shall be symbolized by any image of the sight depends upon the mind of him who sees it."
-- Oliver Wendell Holmes, Jr.