Convert your Motronic 1.1 or L-Jetronic balancer to a Motronic 1.3 trigger wheel. Comes with brackets to mount the crank position sensor. You can purchase the sensor itself optionally.
You may need to stick the ring in the oven or on the BBQ to expand the metal. Make sure the balancer is cleaned off thoroughly first. Just a few tacks will suffice, it does not need to be welded all the way around.