[wingnut60]

rouxguy,

5500# max tongue weight--is this the stated payload capacity?

You are going to have to do some more homework...first, you will need to actually weigh your truck (need both axle weights also) with as much stuff as possible that you would have in it when towing. Only then will you be able to know the actual payload number. Once you have this number, you will be able figure max tongue weight/rear axle capacity based on the Gross Rear Axle Weight by GM for your truck.
Actual truck weight taken from the Gross Vehicle Weight Rating will give you the remaining payload capacity, which should also be near the amount available for tongue weight of a new trailer. Once you have these numbers, you can think about what size/weight fiver you can handle.
Lots of fun, eh?
Joe