Old Air beats anything I researched ... rather than repeat myself, here's a cut & paste from the other AC thread here:
I just installed the Hurricane AC/Heat/Defrost unit from Old Air in my '54 ... the install was fairly easy, instructions were great, and the unit works like a Hurricane! 3-speed blower, temp control, defrost and/or heat control, and a plenum that hugs the line of the bottom of the dash perfectly! I am tickled pink. The heater pumps more heat than I ever dreamed of and the AC pumps more cold than I ever thought it would. What more?
The interior unit (I guess that's the evaporator?) sits right behind the 4" firewall hole ... you do NOT see it like you do the original heater, which is just above the passenger's feet. You definitely loose some of the glove box, but nothing worth crying over. I'm gonna buy a new glove box (they're only $11) and do some measuring for different depths, left to right, and customize it to fit so I'll get as much space in there as possible -- the right side of the glove box is where I've lost the most ... it might only go 3-4 inches deep there, whereas, on the left side I may have only lost 3-4 inches in depth.
You can see my install at the link below my sig ... If you want specific pictures, let me know and I'll do it for ya.
