Ken the tank bushings just press into the holes in the bottom of the tank. I put a little grease on them, push them in then a little grease around the shut off valves and push them into the bushing. The stem on the shut off valve expands the bushing for a seal. While you have the valves out disassemble them and clean them out. I've probably done at least 10 of these things and every one had plugged valves. I also replace all of the fuel lines with 5/16" hose and decent clamps. Keep in mind that these tractors are all 20+ years old and the rubber they used back then was not made for the fuel we burn today and it rots from the inside.
