Sweet!    Have you asked that dude with the super clean cb in his sig line where he got his bitchin full system?  It looks like a really high quality newer setup more like you'd find for my bike, so I wonder if it was custom made or if there's enough of a following for these that somebody is making a serious exhaust for them now?  Either way, on the older bikes like this it's a lot easier to see big power changes from exhaust than it is on a newer bike like mine, and I bet you could fab up your own stainless system fairly easily and help pull all the potential there is out of that engine!!