Have you sorted out footpegs yet? It occurred to me that you might benefit by using the tapped holes underneath the engine as a footpeg mount, much like the XR50. This is an example of what I mean, although this specific mount is not likely to fit:
http://www.ebay.com/itm/Footpegs-Mou...336d55&vxp=mtr The pegs could easily be swapped for something more period correct, once the mount is in place. it would be ideal in terms of proximity to the shifter.
That setup not only gives you a footpeg mount, but also a kickstand mount. If you can't find what you're looking for online, it would be simple to fabricate. I might have a pit bike footpeg mount laying around, so I could compare it with a motor like yours if that helps. let me know.