Here is the spark plug needed for Briggs and Stratton Intek and Vanguard engines as well as the spark plug cross references:
Intek — single and twin cylinder OHV 
Vanguard — liquid cooled three cylinders, single cylinder OHV engines and 31 HP OHV V-twin.
Champion: RC12YC
NGK: BKR5ES
Megafire: SE-12RCY
Torch: K5RTC
The spark plug gap on these plugs should be set at .30.
