92 OCC fuel tank flange repair

Hello

Dropped gas tank to replace fuel pump assembly. As I was loosening the nuts holding the pump to the tank, I noticed the entire assembly, lifts off the tank on one side. took assembly off tank and seen that the flange with the studs is not sealing on one side. I could not find any fasteners to attatch flange airtight to tank. I do not know how to remedy this. Can anyone help

Pics would help.