1. Go for 6" susp. lift and 3" body. It'll be good on the whole tipping issue AND be kinder on you U-joints

2. (this is where I'll probably be argued with) I know, I know its really cool to be able to say "yeah, I gots me some 18" kickers" but IF you are by some miracle actually interested in having a awesome SOUNDING system you'd be better off to going with 3-4 high quality 8" woofers or 2 high quality 10s . I can explain this if you're interested, and yes, those 8s will rattle you teeth thump your adams apple and make the "fly-honeys" across the parking lot earrings shake. (The key here is "high quality" and that doesn't always mean popular brands)