Looking to add something to my 2009 chevy suburban with auto leveling, to take care of the sag when attaching my trailer

 

no idea what your towing; why not a weight distribution hitch?

 

Sumo Supersprings is what I use. Love them! I installed them myself. Easy job.

https://www.supersprings.com/shop/SSR-204-40/

 

Be careful about adding springs. Depending on what you're towing, you don't want to overload that rear axle. I had the autoleveling shocks on my '01, and I think the lack of sag had me overconfident about how much trailer I could tow. I broke two rear axles towing heavy trailers.

Make sure you get yourself weighed, to make sure you're ok on your weights.

 

I'm pulling a 5500lb (dry weight) travel trailer. I figure that my ready to go camping weight is no more than 6500lbs. The door sticker says 8200lbs is my limit. The sumos just keep things flat and level.

 

6500 lbs is a lot for a half-ton. I broke rear axles towing trailers that heavy.

There is nothing on your door sticker(s) that says anything about a trailer weight limit. You might be thinking of your 7200-lb GVWR, which is the maximum weight limit for the four wheels.

What you should really be concerned about is the 4000 (or 4200) -lb rating of the rear axle. You'll exceed that before you get anywhere near your "trailer limit." Especially if you have a large (or heavy) family/passengers.