The firewall has a different hole right? Has anyone done this before?
Thanks

I think the firewall is the same, but the pieces that mount to the firewall are different. you need the suitcase which holds the evaporator core and protrudes out from the firewall. I am not sure if the heater core and inside heating ducts below the dash are the same or not.

On the the firewall is different,the hole for the a/c is smaller than the non a/c.You would have to weld in a piece of metal or change the firewall.

You might need to alter the Astro Venilation that was used on w/o/a/c cars.

A person who really knows what to look for, and has a keen eye for detail, can see what's going on here. Even the most critical observer doesn't seem to notice unless I physically point to the area.

Uploaded with ImageShack.us

On a 69 the firwall hole is completely different. Look up vintage air. here is the manual for the 68. I boughtr one for my 69. am installing soon.
http://www.vintageair.com/DownloadsSection/Surefit/Pontiac%20Passenger%20Cars/1967-1968%20Pontiac%20Firebird%20(Inet).pdf