I rebuilt the stock A/C in the Barracuda and it blows decently cool for temps up to about 90 degrees, after that it just can't keep up. And that's only if its been sitting in the shade or the garage, etc. If its been sitting in the sun, forget it. If I had it to do over again, I wouldn't have worried about keeping it original and just put a modern vintage air system on it I'd be miles ahead. I might consider putting a more efficient A/C coil on it, but I've sunk a bunch of money into A/C for it not to work any better than it does.
The Roadrunner has 440 air conditioning right now, All 4 windows rolled down at 40 MPH. I drove it for years with no A/C, black vinyl top & black interior. No more, when I get it back on the road for good it will be sporting A/C for sure.
Later, Jim