Don't do it. I mistakenly bought a 'half ton towable' 5th wheel for my 2011 Sierra 1500 4x4 Ext. Cab Std. Box 5.3L V8 3.42 Rear that had a reduced payload from other Sierra's most likely due to the 20" wheels and P-Rated Tires. My payload was 1601lbs. My friends mostly identical Sierra has a payload rating of 1790. The difference? He has 17" wheels. Anyway, the 5th wheel we bought has a pin weight of 1215lb. with a dry weight of approx 6900lb and an GVW of 8200. It is much lighter than the TT we were pulling but not doable with the 1500 Sierra. Anyway, I ended up buying a 2015 Silverado 2500HD Crew Cab Std. Box 4x4 Gasser on July 17th. Payload Rating is 2831 lbs. on the new beast.