Newbie here starting my 1st A body and need a/c help

Classic Auto Air has been around a while. They are as good as you can get. The techs will walk you through what you need help on.
my suggestion is, if you're under restoration, is to seal/weld up all holes and start fresh. Their kit will not use the same holes. This is common in all aftermarket kits.
They are very efficient in the heat and cool sides.
You can also keep your factory heat/air and go aftermarket condenser &/or compressor. Your choice. that's what I did and have a great cooling a/c too. I live in Tampa and can keep cool all summer long.
If you ever think about going 6 pac(smallblock) there is only one option. The Bouchilon brackets and shorty Sanden(7312) compressor. Classic Auto Air can set you up with this also.
You can download/send for their instruction manual for a heads up on installing.