This is an easy Saturday morning project. One of the problems with old cars is that the seals around the heater doors disintegrate. On Chevys, it means that the hot air from the heater is always blowing into the passenger compartment. That's a problem when it's hot outside. On Hondas, it means that when you get stuck behind a smelly Ford diesel, the REC button doesn't stop the stink.
To fix that problem, pull out the glove box, then the heater blower motor. Complete directions for that are in the manual (you can download it from my signature below). Pull out the air diverter doors and reseal them using some standard foam sealing tape from Home Depot. Also reseal around the top of the blower motor (see the pic). Everything you need is pictured below. The only tricky part is that one of the doors can be turned end for end when you re-install, which will cause problems when you try to re-assemble the linkages and re-install the box. Just make sure your mechanism works completely before reassembling. You'll notice that your AC works a little better and that stinky Ford pickups don't stink so much anymore.