The SS actually handles really well from the factory. It's really a little too stiff for our POS roads. It would be a waste doing much to try and improve the handling. The biggest issue with lowering is if you have to deal with speedbumps anywhere. My parking lot at work has them so no way I would lower. The headers on my 70 SS396 already scrape on them at work. Lowering will make it look better but the handling won't improve a lot over stock. If you're not planning on autoxing the car then don't waste too much time or $$ on the suspension/handling improvements. The best handling improvement you can make is putting on a trailer hitch!
It actually bolts together the whole rear frame area much tighter and you can easily feel the difference. I'm not sure what the law is on tint % here in NJ but if you go too dark you will probably get hassled and might not pass inspection.