I don't think there is anything particular about a Northstar compared to any other heavy truck camper. It's hard for me to believe your truck only goes down 1 inch with 3600 lbs on it unless you have airbags, supersprings, or timbrens, but let's assume that's right since how much it goes down has little to do with anything.
In any case, the normal mods are shocks, some type of bump stop addition, and 19.5 wheels and tires. Northstars site says 3176 base dry weight which is about what my SRW was rated at for truck campers. I think a reasonable "low" estimate with water, propane, batteries, people, and some stuff, and some options is 4500.
You will be pushing the tire capacity pretty quickly. So, I'd say 19.5s, Bilstein 4600s if that isn't what you bought, and upper/lower Torklift Stableloads.
Take a look at this thread. User "thedavidzoo" just put the same TC model on a RAM DRW.
http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/28937969/srt/pa/pging/1/page/1.cfm