The manufacturers GCWR isn't placarded on the truck anywhere nor is it a fed reg to even be on the truck.
Its not a enforceable number as its impossible for road side leo to determine what any trucks GCWR is. It has no legal status when using the truck commercially or non commercial.
This email from a California size and weights CVEO pretty much sums up legal weights issues will be the vehicles axle/tires for a truck pulling a RV; "snipped for length"
Q: “Many of the owners travel over their tow vehicle GVWR and /or
GCWR. Are there any state laws against this? Or does the owner just
take the risk if they wish?”
A: The California Vehicle Code (CVC) does not contain a law that
specifically limits the amount of weight a vehicle may tow based on the
towing vehicle GVWR or GCWR. There are, however, laws that limit the
amount a vehicle may tow based on other criteria.
Section 1085(d) of Title 13 California Code of Regulations prohibits
the loading of tires above the maximum load rating marked on the tire,
or if unmarked the maximum load rating as specified in the applicable
Federal Motor Vehicle Safety Standard, or in a publication furnished to
the public by the tire manufacturer. This would most likely happen in
the case of a pickup truck towing a large fifth wheel travel trailer, as
those types of trailers tend to transfer a larger portion of their
weight to the last axle of the towing unit causing that axle to exceed
the tire load limits.
Section 24002(a) CVC prohibits a vehicle or combination of vehicles
which is in an unsafe condition or which is not safely loaded and which
presents an immediate safety hazard from operating on the highway. This
section provides officers the authority to stop a vehicle or combination
of vehicles that is, in the officer’s opinion, unsafe to operate on
the highway. This section could be used to prohibit a driver from
continuing until the unsafe condition is fixed.
I trust this has adequately answered your questions. Should you desire
any further information, please contact Officer Ron Leimer, of my staff,
at (916) 445-1865.
Sincerely,
S. B. DOWLING, Captain
Commander
Commercial Vehicle Section"