Good for you for doing your research and asking questions. I've never seen a FW with GVWR TBD. All towable vehicles I've seen have the GVWR posted on a sticker on the outside of the coach along with the tire size, pressure, etc.
GCWR is Gross Combined Weight Rating. This is the associated with the TV, and is total permissible weight of the TV, FW, including passengers and cargo.
There are a couple key items when considering a TV. One is towing capacity. Let's say for example that you have a 12,000# towing capacity, and the GVWR of the FW is 11,000#. You'd be fine.
Another key point is payload. All TVs have a payload limit. It's usually listed on the tire placard on the door post. Payload consists of everything you add to the TV. It includes passengers, cargo, pin weight, FW hitch, etc. You could have met the towing capacity of the truck, but still not have enough payload to be safe.
Of course, there are other items such as axle ratings to consider also.