Early Vent Door Hinge Repairs (and Kryptonite rivets)

Haven't found a circa ABody yet with intact door hinges on the vent/heater boxes. Not sure yet how to repair the hinges, but I have an idea in mind. First off, decided to remove the door. Those are definitely not aluminum rivets, had to fight tooth and nail with various drill bits and Dremel tool accessories. What's the secret, how do you all repair the hinges anyway?

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