If I had some info on the welding up & remachining of a twin plug head to a hemispherical chamber like shown in VMX #43 I would be tempted to do that at work but instead I've got a 74 model head coming, looks like the pocket would be the same as the earlier models
My memory of the front plug fouling with the dual plug ignition was that the bike almost wouldn't run, still having the standard Jikov may have also had something to do with it. It would always involve stopping & holding the throttle wide open until things cleared out