How Good Is My Air Conditioned Memory?

[1972RedNeck]

It is hot up here in Montana. 85 degrees. 83 degree heat index. My mind might be fried.
If my memory serves me correctly, there is a door inside the A/C box that diverts air to/away from the heater core? Is this correct? Is there any place to buy a new door/ A/C box? I know a door is broke and I repaired it with popsicle sticks/Gorilla Glue. I think this is leading to the air being not as cold as it should be. I have to run on inside air to shut the heater valve off because it blows hot air if I don’t. Any ideas? Suggestions?