Here is a little tidbit to maximize your total A/C system, when you get to this portion of it. Find a 1986 or 1987 B2000 (maybe the 1988 B2200 also) and get the "blend box" that is above the blower motor, and that the blower motor attaches to. It has a much better designed blend "flap" that seals up way nicer! And they last 10 times as long as the "foam" covered flaps!
Pics of the earlier ones, compared to the later "foam" design.......the unit on the left is the later design, that has a layer of foam only.......yours has lost all of it's foam already I would bet......or if it is still there, it will crumble when you touch it!
The earlier unit has a vinyl covering over the foam, and is usually still very flexible.
When that foam one loses it's foam due to age, it doesn't seal up too well anymore! So you will always get some outside air coming into the system......even when you don't want it!
As you can see in my pics, I also replace the foam that is falling apart on all of the pieces and parts when I restore the A/C system in my trucks......I get the heater box flaps as well.
Don't forget the vent seals either! 😉
