Looks like you probably have access to the back side of a bunch of them, so you might want to read up on solid rivets, or "bucked" rivets. VTS sells everything you need, including the larger 5/32 solid rivets that have the smaller, matching head. (usually you up-drill from 1/8 to 5/32 if the hole gets to big). You should only use Aluminum rivets. Be sure any blind or "pop" rivets dont have a steel mandrel. Here is VTS info:
Solid Buck Riveting
Do a search for Buck rivets or Bucked rivets and you'll see lots of info. A 3x rivet gun can be had on ebay too for less money.
Be sure to reinforce your AC opening if its not already. I did that and it was some work, but very rewarding.