I've heard iffy things about the MSS kits. Some say they were trash, some say they fixed the issues that existed. I don't have any first hand experience with them, but I'd do some due diligence (if you haven't already) on that. 3 car garage sounds like paradise, just need to get a lift in there!
Yeah, there are a few design revisions - longer front springs, revised rear adjuster design, etc.. If you want to lower the car significantly, it's NOT a good kit for that, and their marketing did a bad job of reflecting that. Since I want a minimal drop from stock ride height, it's a decent option, although I'm hopeful they'll share spring rates (they might not). I like the helper spring in the rear as a way to run higher spring rates without destroying DD ride quality. It will also give me the ability to drop in hypercoil or swift springs to play with spring rates, which is a big benefit (although annoying to do on the front).
As for the garage, it already has a high ceiling and a high lift garage door.... but sadly no lift. The question is do I get a project/weekend car before the lift, or a lift first? I gotta lean towards the car... and for what we're spending on thehouse, that's DEFINITELY at least a few years off right now!