What can I tow with my Suburban

I agree with lawrosa, it seems to be a cooling package that may account for the low tow rating. It might be just a cooler that can be added, but may be a larger radiator also. You can check with your GM dealer to see what is needed to increase your tow rating. A thousand lbs of trailer wt will not make a lot of difference, until you start towing uphill. It is mostly the wind resistance of the trailer. With any full size trailer, it will help to improve cooling. The tire loading sticker on your door post will show a payload not to be exceeded. Your hitch should show a maximum as well.

Jerry