Dude, plastic weld it up. If it was plastic that is. Did you get the replacement Rolls Royce part or what? LOL
My original plan was to plastic weld it. But were the crack in the side of the tank it sits on a bevel on the tank between the top and the side of the tank. When the mounting strap was overtightened it pushed that flat bevel inward basically caving in the center of that bevel.
First picture is suppose to be what the tank looks like, second is what happened when the clamp strap pushed down on the top of tank.
So there is no way to prevent the pressure from the strap from trying to push the bent area inward recracking the tank. Also the tank also has stress cracks around the fuel level sending unit hole mounting studs in the top of the tank. Keep in mind this is a 15.3 gallon tank from a 45 HP tractor