[H2Much]

You should be able to get a few, maybe 2-3 inches or so from the keys. Too much mroe and your ride becomes "unsafe", offroad shops will tell you that if you have them cranking them as it makes the front end not control itself very well.

If you are getting the bigger tires, (37's, right?) ride quality shouldn't be an issue. Tires will suck it up.

On the ranchos, can't help you there. I went with Bilsteins myself, so no opinion. With the rear, plan ahead as you are going to run into issues with the air system calibrating properly unless you go with coils. Spacers will throw off the calibrating arms on the sides and over time, will jack up your air ride. Some haven't had issues, but most have, so just be looking into that ahead of time. Ask GM dealer if they are familiar with calibrating those arms for airride balance on lifted vehicles. Once lifted, you will need ot have those arms recalibrated so that your airride functions properly. If they don't know how to do that, find someone who can, otherwise you will have issues, and it is not fun. Just my 2 cents based on my experience with this.