Nice ride man! I almost bought a skyroof off Ebay awhile back. Someone was parting out a 2-door and was willing to cut it out for me and ship it, but the shipping price ended up being astronomical and if it wasn't in California, I would have just picked it up. I might still go that route eventually though. Another wild idea I had for my Caprice was building a t-top roof. To date, as far as I know, there's not a single 77-79 Caprice/Impala Coupe t-top on the planet. It's kind of a back burner/dream of mine. It would require a ton of modification, including the doors. It would also require some huge t-top panels.
As for adjustable suspension, I too am a bit of novice when it comes to air ride, I was more of a hydraulics guy back in the day, but I've been studying up on the air ride systems for the past few years and trying to decide how I wanted to do it. Basically, since I'm doing a frame off restoration, I'll be building my entire chassis with the air ride system and all while the frame is off the car. Even though I'm not doing hydraulics this time, I'm still going to box the frame under the doors and reinforce the rear arches over the axle to make the car solid. None of this convenes until I get the new floor pan welded in and the package tray fixed, then the body can come off and the real fun begins.
The 91-96 Impala setups from Ride tech I believe are a good choice for these cars. For the most part these systems are completely bolt on and require no welding or cutting. They don't list our cars specifically, but I can assure you, whatever they make for those years will go into any b-body down to 77. There are a lot of options, but for a cruiser and being able to raise it/lower it, I think the Level 1 is where I'm leaning. Although, they have some front setups where each front bag is donut shaped and the shock goes inside of it using the stock shock mounts from a-arm to frame and I kind of like that better. I think I'm going with upgraded tubular upper and lower control arms too. One thing I'm going to be looking into are silencers and an engine driven compressor. I can't stand the sound of the air escaping and the noise of those compressors. I want it all silent. Another thing I want to achieve is to have everything hidden from view as in no exposed tank/lines in the trunk.
I wish I could help you more on the install, but I've yet to embark on that. If you were doing hydraulics, I could explain exactly what to do from start to finish right here in a few paragraphs. I'm done with hydros though.