The following are diagrams courtesy of Tmoss & Stang&2birds
HVAC vacuum diagram
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring; http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.
“AC only blow out from bottom”? I was ready to answer a medical question! Can you turn that into a circus act? :-0
Jrichker has you covered with the serious answer. Vacuum lines, rubber or plastic, can be getting brittle by now. I have patched a nylon one with a new rubber line that fits well over the nylon and holding it with 3-M weatherstrip glue of death.