All of the spec sheets I've ever seen for a Gran(d) Sport(s) show DB main tubes and 531 forks. Earlier spec sheets don't show 531 stays. All of the GS frames I've ever seen have a 531 sticker on the forks.
Pretty much everything else is up for grabs. I have a Gran Sport, a Grand Sport, and a Grand Sports decaled frame. I've got one so modified it has it's own, unique model name.
