Hello Rich -- Welcome to the Forums!
A question about GCWR opens a large range of issues pertaining to adequate tow vehicle for the intended trailer. As a reference for others, a starting point on this topic might be Airstream's FAQ page
(though there are many sources).
Factors to consider in loading:
GVWR of trailer
GVWR of tow vehicle (TV)
Payload of TV is not a stand-alone figure like the above 4 -- payload is GVWR minus the base or curb weight.
Submitted for your approval, approaching the max of either tow capacity or GCWR could put you over the line on TV GVWR.
Manufacturers place one driver into the TV to determine tow capacity -- and that is the base model as specified, without options or add ons (like additional passengers, truck caps, cargo onboard TV). Therefore tow capacity is the heaviest
trailer under optimized and unusual conditions. [on edit: I'm not implying that this method is used for GCWR.]
A trailer will have tongue weight equal to 12-15% of its gross weight. This is only an approximation until you'd actually weigh it. Weight distribution gear does little to change this. Tongue weight is a load on the TV and must be added toward its GVWR. And of course figure in the approximate weight of passengers, TV accessories and cargo.
There are many layers to this onion. Like 2air' I'd suggest that you give us some examples of what TV-Airstream combinations you are considering. There are so many hypotheticals that this could descend into chaos...