On a stock A/C car, the vents are in the lower dash, which is a bolt in, replaceable part, and the dash pad, which is also a bolt in, replaceable part. Worst case scenario is that you'll have to cut one of those two, but the good news is that replacements are readily available in the event of a disaster.
1970 Mach 1 M code
1990 5.0 LX Limited Edition
I keep noticing the DOT puts up signs to honor my burnouts. That's nice of them.