Tom,
That does narrow the scope significantly! Basically, there are a pair of posts that attach to the frame to space the footrests out to either side at the lug at the bottom of the saddle tube. A long bolt through all clamps everything together. The rear brake pedal pivots on one of these posts, as well as the centerstand. I may be able to help with drawings of the footrest components as I did have to replicate these items for my A31. The originals were too worn and rusty to salvage. Where the posts attach to the frame, there is a shallow key slot. This is often damaged because the footrest bolt is not kept tight. Also, the centerstand puts a considerable bending load on the posts, stretching the bolt, and causing it to gradually become slack. I will look for some drawings and post a picture of the relevant area of my A31 frame this evening. My A31does not have the engine or transmission fitted, so it should be clear to see the arrangement.
-Doug