I have used Classic, Vintage, Old Air, and defunct HotRod air. In my opinion, Vintage is the best of them. Now, I do feel they are not as good as OE but parts for these are rare. The major problem with all of these aftermarket A/C setups is that the water valves don't function well enough and hot water continues to run inside the box. We have just started installing a ball valve in the heater lines to positively stop hot water from getting in the vehicle. It works, we have all black, Big block powered cars running A/C in Carolina heat.
As far as Classic doing resto work, Never again for me! I had a super rare 1960 chevy Impala in years ago, and sent them the A/C stuff for there "professional, meticulous factory restoration" I was told how the lines would be cut open, and tig welded for perfect factory appearance. After about 8 months, I got back some universal crimp-on hoses. Absolutelty disgusted with that outfit. Ruined the car as far as correct parts. Factory air on that car is so hard to find.
Pretty much Vintage air or nothing nowadays. Thanks for the input, just lookin to see if anyone had done a C-body