Yes, the 7650 or 7700 GVWR (could be different numbers if the OP is talking about a 4x2) will tell you what you need to know if you are looking at a SCAB or SCREW. But if you want piece of mind, the window sticker generator in post # 7 is what the OP needs. You are absolutely right to be asking how to verify this. Be aware that many are told "Max Tow" when they are really 535 (AKA the normal towing package).
I would also check FordEtis also. FordEtis home page
Put in the VIN and hit search. Then click the little down arrow on the lower right where it says "Minor Features".
That will give you the build details of the particular truck including just about everything you could ever want to know. The details should say "With Load Leveling Trailer Towing" for a 2011.
Disclaimer for all the Canucks: Unless the truck is Canadian . . .The original sticker having Max Tow mirrors listed is a near certainty that it is a Max Tow equipped vehicle. You can verify the 3.73 axle ratio on the sticker also, or you could look up the code on your door. A Max Tow requires the vehicle to have that ratio. Then you can check the code against this chart (2011 version).
As someone mentioned, the 36 gallon gas tank is a must in my mind. The 26 was a source of many complaints on the early models (ie 2011) on the F150 Ecoboost forum.
If I understand the discussion above about HD vs Max Tow. . .I am fairly confident the HD F150 SCREW in 2011 was a Harley Davidson. I beleive the first HD Heavy Duty (SCREW) package was an option in 2012. All SCAB/SCREW heavy duty payload packages (2012-2014) should be GVWR 8200.