SSR is based on the Trailblazer XT frame, shortened 13" Trailblazer with the 5.3 is rated at 7200 lbs - the frame, transmission and engine could handle it, but the hitch system was designed for light towing. I would get a Trailblazer hitch cut and re-fitted to go through the license plate frame. Lots of room to work, seeing as there's no tire to worry about. You might have to work a bit with the battery box location, and you'll need to blast out the factory hitch set-up. You could probably go with a stock hitch under the rear panel, but it wouldn't look as clean.
Capacity on this truck is more of a tire and spring issue. As an example, our Sonoma had a 5000 lb tow capacity, but the same frame, engine and transmission combination on a Chevy Extreme is rated at "0". We added some airbags, and it tows great for short distances. Definitely prefer the Duramax for longer hauls. Photo of the hitch set-up on our Sonoma follows.
The towing capacity is constrained by the tire load rating and the cooling system. An electric fan system replaces the engine mounted fan. The shortened front of the vehicle does not allow a Trailblazer cooling system.
The towing bar is a neat setup - as long as you stay withing the engineered parameters - for 2500 lbs. max load. I wouldn't want to attempt to drop a 5500 lb boat on it. There's a lot of leverage on that system.
However, it you do set it up properly with a trailblazer frame mounted hitch, the SSR frame, engine and transmission are the same as on the Trailblazer. It should be able to handle the same load - 7200 lbs plus whatever the base weight differential is. I can't find a weight for the EXT in the brochure, but with 13 inches more frame, 2 extra doors, four extra seats, a roof, and a rear window/gate combo with all those extra electric motors, it should be a little more portly than the SSR - therefore even more potential tow capacity.
You may want to limit the tow distance and keep tabs on engine temperature initially to make sure you don't have an issue. If it's all go, the next step would be to attempt some gradually increasing hill climbing to see what it's capable of without heating up. Some of the locals in the rod club do a fair amount of towing - they are mostly equipped with electric fans and seem to survive quite nicely.
I have a Sonoma that tows fine for short distances, mostly to car and boat shows. It had a 5000 lb tow capacity. A friend's Chevy Extreme extended cab (same frame, engine, transmission and weight) was rated at "0" tow capacity. A set of airbags did a nice job of levelling, and it tows just fine. His tire ratings were actually higher than the factory tires on mine.
He's been towing a ski boat for 4 years, and the local dealer has never had an issue with warranty on his truck. The dealer thinks the whole "0" rating was a bit of a crock.
The whole tire thing gets blown out of proportion. A 5000 lb boat will only add a maximum of 500 pounds down pressure on the rear of the truck, so 250 lbs per tire - I can't imagine they cut it that tight on the safety rating for the tires.
Bottom line, it's your truck, and you should be able to make it what you need it to be. The whole Hot Rod mentality is to play and experiment, and make vehicles something more than they start out to be. This is the ultimate factory hot rod - have fun.
Thanks for the info, I appreciate it. Having considered the total affects of this matter, I have decided to trade my truck camper for a cool little Casita 17 ft camper, which weighs in at a little over 2300 lbs. This frees up the Silverado to handle the boat on the trip from FL to KY. It also gives me the opportunity to drag the Casita behind the SSR. Talk about head turning!!!
Still looking for somee one else to get an SSR in West Central FL. In the last 30 days we have not seen ONE other SSR, and have met many people who have never even heard of one.
This is unique and a real thrill. Hope you can experience it.