I won't argue with an owner (my own personal experience only extended to the 70s type 2s, not 80s) but I'm surprised. The source I checked didn't show a model over 3500. It's estimated for the campers, but 1k lbs is a hell of a margin.
It doesn't mention Westfalia models directly, though, unless they're one of the model numbers in the breakdown.
http://vanagon.com/info/years/1981/index.htm