Doug, I use CH Ignitions on all my conversions. I also use the Bosch cap. I also use NGK plugs. Personal preference. So on that setup I use either NGK BPMR 6A or BMR6A. These plugs have a 3/4 hex on them. Champion also works and that number is RCJ7Y. On the rubber boot electronic ignitions from CH I have used RDJ6J and 7J. Never have I seen any discernable difference in plugs. Gap mine at .023.

Tim