Carburetor confusion

I have a 18hp Briggs engine model#350777-1154-E1 that I am working on for a customer. I work on lawnmowers and such for the general public, and have been for years. This motor is on a John Deere GT235 riding mower. It had caught on fire and burned a good bit of stuff in the carb area. The guy that owns it has fixed most of the damage but did not know exactly how the carb was supposed to hook back up. Of course I am going to rebuild the carb but it has three ports on the left side and I know the center one is the main fuel inlet, but do not know what or where the other two are supposed to hook up to. I think one of them is a vacuum line but still don't know where it should hook up. If any one could PLEASE help me with this dilemma I would be most GRATEFUL!!

 

The one big one is the fuel inlet, the one just over the bowl is a vent that usually has a short tube that hangs down but it's not necessary. I'm guessing the third is the one at the bottom of the bowl? If so, that is a bowl drain and doesn't require any attention.