how to install a gas tank on 3HP Briggs

I have had this motor for a long time sitting on a shelf and i decided to get it running and use it. The motor came off of an old wood chipper i believe the motor is from 1973 or 1974 so i put it on an old lawn mower deck laying around off of an old lawn mower. It had bevel gears so i could put a normal go kart engine on it so i built a hitch and put some read wheels on it and pull it behind my 1984 ATC 200s