An A3 Motor has lots of differences. Have been looking at this recently as per posts and reply's on this board. I am not going to use the A3 Motor I have but, replacing with an A1 A2 set up.
The A3 motor from what I can see will only operate with the A3 IC Ignitor, and Pick Ups, you can not match any others to it. The Block is different, Engine casings are different, Pick ups mount left side of crank to the correct casing. There used to be an excellent description on this site, which I down loaded a long time ago. not sure if it would upset anyone if I re-posted it. someone put me in the right direction because it was produced by the previous owner.