I need help with 14.5hp briggs OHV

I got a free 14.5 horse power briggs from a Sabre riding mower and I mounted it on my off road racing craftsman I cleaned out the cylinder and the carb but it didn't come with a spark plug so if any body could tell me what type/ model number spark plug to use also the is a electrical plug on the bottom of the carb and the plug is on the drain plug/ bowl nut but anyways does anyone know what that's for?

The spark plug should be a RC12YC (Champion #)
The thing under the bowl is an anti-backfire solenoid. It needs 12V to operate; the engine won't run if it's not working.

We have ran a couple of those engines. Removed the fuel soliniod and replaced with a plug, they tend to go bad. Also they would foul plugs, so got a hotter plug for it, parts store can tell you what plug is hotter. They will blow oil if you run high rpms. Strong motor, plenty of power.

Thanks for the help with this motor i will be posting my build on this site. but about the fuel solenoid, I couldnt find a plug that fit in there so either where could i get one or how should i hook 12 volts up to it for it to properly function?