[JL8Jeff]

That's fine for brand new metal, but once the metal rusts like that you'll need to either surface those mating flanges for it to seal or get some sort of gasket. I would just take the spacer down to Pep Boys and go through the exhaust gasket section. They have a ton of gaskets so it shouldn't be hard to find one that works. Otherwise you have to get them perfectly flat and level to seal up.