It's really a pretty reversible process; i.e., you can remove the aftermarket air systems and go back to the original look with little effect on the car. I bought an Old Air Products system for my 66 several years ago at the Knoxville show, but never got around to installing it, as my 65 has factory air. Just decided to drive the 65 when we needed air. It's still in the garage just in case I should change my mind.
But, as best as I remember from the installation instructions, only takes a couple of holes thru the firewall above the carpet line on the passenger's side to install. These are repairable in the future. Also, the cross braces on the radiator support must be removed for this system, the condenser goes there and provides adequate bracing.
If I didn't have the air setup, I'd definitely install it on a driver.
My thoughts . . . .
rlm