I am far removed from being an expert, especially in the "softer-side" of things.
Our '05 Sun Voyager bed spread is supposed to be 60 x 74. It is provided by Decorator Industries Inc, Abbotsford, WI (800.678.5423). There also seems to be a 60 x 80 size used on a few coaches (very few).
You might want to call Decorator & see if they can help you. Their website was not particularly helpful:
http://www.decoratorindustries.com/ There is a "contact us" link.
Bed dimensions per Bed, Bath & Beyond are:
Twin 39 x 76 inches
Twin X-Long 39 x 80 inches
Full 54 x 75 inches
Queen 60 x 80 inches
King 78 x 80 inches
Cal-King 72 x 84 inches
I'm thinking that these numbers suggest that the norm for Gulf Stream beds is queen size, perhaps short queen (60 x 74) or standard queen (60 x 80), but queen width.
See what Decorator Industries has to say about sizing in the RV industry.