Don't sweat it!!
Pretty much... As long as the combined weight doesn't exceed 26,001 pounds OR have any placards, you should be fine in
most states... Most or (all states and provinces) will require a CDL only
IF you are towing or hauling for a profit.
Some states, however, will require you to be registered for the combined GVWR and some do not. UT, for instance, automatically registers everything from the worn out early '80's model Chevy Luv, Ranger, Mazda, Nissan, etc... all the way to an '11 Ram 5500 for 12,000 pounds (personal vehicle NOT for hire)! You can register ANY truck up to 26,000 pounds (in UT at least) if you really 'think' that you need to.
WY, on the other hand, only allows up to 10,000 on a truck or passenger plate and ANYTHING beyond that will require you to get a 'commercial' or 'apportioned' plate. (I asked)
My '92 W-350 is technically "overweight" in this state by a few pounds by simply having a truck plate (keeping the GVWR for an empty truck in mind). That said, ANY fine assessed for personal use by exceeding the combined weight or requirement to have ANY class of license (above John Q public driving a Mercedes) by hooking up to a 5er or TT for the weekend, would be thrown out of court before the judge even seen it!!
Both the CDL manuals for WY and UT clearly state that you are exempted from the CDL requirement for: recreational, farm equipment, fire/rescue equipment, and military. My EX-wife has driven a fire engine (for almost a decade) that's rated around 55,000 pounds and has never been required to have, nor ever been asked to obtain a CDL
BTW... My EX-mother-in-law works at a UT port as well as my EX-brother-in-law (I always ask either one or both of them exactly what
they're looking for)
Next time you end up in a truck stop, just ask the guy in the 40' Monaco or the guy driving a Prevost bus (both have air-brakes) if they even have an endorsement on their driver's license for air-brakes... And more importantly, if they've ever been stopped, fined, or harassed by local or state police for NOT having a CDL.