First, my Heart and Prayers go out to All affected by Hurricane Harvey, My Wife's Family are in the Tomball area of Houston. They are OK.
There was a similar question earlier this Month - About Putting A/C in a First Gen.
It has some Info and Pics along with other Members input.
Systems are almost a Pick your Favorite, I went with the Classic Auto Air system.
No I do not have a Convertible, but I do have the BB and Headers - Big Heat Soak coming from the Engine/ Headers and I put the Heat barrier/ Sound Proofing and a New Jute Pad on top of that - I can still feel the Heat coming up from the Floor.
Where I was in a position having my car completely gutted, I chose to add the Creature Comfort of Air Conditioning.
Some of the Stocker's/ OEM cars like the 375 HP's and Z-28's and Original with out Air are in for that Original 70's Fresh Air Feel and the 8's and 9's have the Astro Vents, which do work really well until it gets really Hot and Humid.
And there is one other benefit of A/C, When the windows get Foggy, I turn it on and they Clear up, I have been caught in a Shower/ Downpour and I do drive my Car thru the Year as long as the Roads are Clear, No Ice or Salt, and it can get pretty Cold and Damp here in CT.