Here are the brackets I made for my Daytona Special, I used 1/2" T-6 aluminum plate, readily available at Pacific Steel on River Road. I made the pattern out of thin plastic, the cut out the aluminum in my shop. After I made the brackets and installed them with the foot pegs and shift/brake arm, I was able to figure out exactly what I needed for linkage.
When figuring out the placement of where I wanted the pegs, I put a string line from axle to axle (wheels) for the height of the pegs, I sat on the bike and moved my feet around til I found just the right spot. Then it was pretty easy making the pattern just using the stock foot peg mounting tabs. For my current KZ project, I had to make new mounting tabs (well, Amos made me some cool ones on the water jet machine), and weld them to the frame, still using the same method to find the right position.
Does this make sense?