On many conversions, I use a round sensor. You can buy round sensors made up by Adrian at www.ch-ignitions.com. Sometimes l buy them ready made, but I also have a stock of bulk hall effect sensors and I make up my own sensor unit by soldering the wires and then gluing the sensor and wires into a short length of aluminum tube. I then hand form a bracket that looks like an Adel clamp, and mount it to the front of the engine using a single 8-32 serrated, socket head screw and Loctite. Works very well. Then I machine up a collar which is a sliding fit onto the prop hub. This collar has the magnet for triggering the sensor, and a set screw to secure it. This is used to set the ignition timing. I have this setup on dozens of engines and it is fairly easy to do, reliable, and durable.

Once again, I will try to find some pics to post. Keep up the nice work!

AV8TOR