[JandC]

If you are basing you height on what a dealer told you, then to be honest you have no idea how tall your unit is. Unless that dealer had your truck hooked up to your Montana and did a physical measurement then it would be impossible for them to know your height.

I am guessing you are between 13'3" and 13'5" actual height to top of front air. The only way to know is to pull out the 10' step ladder, long level, tape measure, and do it yourself (with truck hooked up).

Even though I utilize the Rand RV GPS I would not blindly trust it while traveling. The only reference I fully trust is a current Trucker's Atlas.