Fresh air vent rebuild....

[EARNHARDT#3]

My fresh air vents were in bad shape so I picked up a good used pair here on the parts board. I removed the rust via an electrolysis bath. I then drilled out the rivets and split them apart. They're now in primer. My question is when I get them painted and put them back together with new seals, what kind of rivets should I use? It seems the blind rivets like from the factory would be a pain to do. Steel pop rivets would probably bend the metal. So I'm thinking aluminum pop rivets and then fill the holes from the back with something. I don't know what the best solution is. Pic just for the heck of it...