Msd opti timing adjustment
The MSD opti base moves the optical sensor to accomplish timing adjustment, again the adjustment is in the base not the cap.
Adjusting it blindly without keyed hub, degreed damper and fabricated pointer is really a bad idea. Setting up to do do it in a controlled manner with new hub, damper etc. then setting up a stable tune to be able to see what timing is with a light would be a lot of cost and hassle and really a poor idea as opposed to using a aftermarket ignition box to do the retard and get the benefits of window switch and spark based rev limit.
What you have is a BAD IDEA, drop it.

