Again, the rules will vary by state. There's a design spec for the interstate and defense highway system (that may be 13'6") based on the height required to transport a main battle tank on a transport. But that's not a state rule
, it is 14'. See:
California Commercial Driver Handbook - Section 1 - Introduction
and you may need a commercial
depending on weight and other issues. There may also be weight limits posted on your route
, you'll need to confirm those ahead too.
You really need to check each state that you intend to pass through. One reason trucking companies charge more than gas money--is because they need to keep on top of all the rules, for all the states, with the changes every year.