Well that Dorman part# checks out and the gaskets look right. Maybe the torque spec is different with the aluminum gaskets--I've never used one myself so I don't know anything about 'em. I used paper gaskets with Hi-Tack to help hold 'em in place and a little RTV to help seal. I suppose if I were in your situation I might try slightly tightening the bolts at the leaky header in the hopes that I wouldn't have to pull the cooler out and try again.