Big Guns can have System 11A or 11B boards
System 11B started partway through the Big Guns run, so check the boards in the game before ordering a CPU or reading schematics. All Big Guns have the auxiliary power driver board and CPU-controlled special solenoids.
Systems
Games
Source: Repairing Williams System 11 Pinball 1986 to 1990, Deel 1, Clay Harrell (pinrepair.com)