Rich--
No, there is no standard full or whole rack. It just means the entire slab, all the bones included. A full rack of spares could be 4.5 lbs, 5 lbs, or 3 lbs, e.g., depending on what size the pig was when slaughtered. Spares in the 4-4.5 range seem to be the most prevalent.
In restaurants a full rack just means a whole rack of ribs, usually trimmed, sometimes St Louis style, sometimes not quite so trimmed. There is no weight standard except, perhaps, within the specific restaurant itself. Restaurant 'A' might always specify a 4-4.5-lb rack size to their supplier; Restaurant 'B' might specify 3-3.5, say.