Dude that's a nice looking interior that you got going on there, nice and clean floor pans.
You have a perfect opportunity here to do 2 things that are cheap, easy and quick. #1 is to apply new weatherstripping around the joints for the air ducts. This will allow for a tighter seal and better air flow. #2 is to clean out the evaporator. Over the years a bunch of junk can fill in there and make the AC a lot less efficient.
pictures speak louder than words.