Re: The Right Horse For The Right Cart
No, the 'Z71' package will probably not increase the towing capacity. A 'Towing Package' might. 4x4 reduces the towing capacity (due to the weight of this option). So make sure you are looking for the towing capacity of your exact truck.
The rated towing capacity for a truck is mostly for marketing purposes. If you look at the fine print, you will likely see that it is with a completely empty truck, no passengers, no cargo, no accessories; nothing but a 150 pound driver and a bit of fuel. Everything above that, comes right off the towing capacity. And that is for a flat bed trailer with 'no' wind resistance.
So as a rule of thumb, you may want to look at your approximate 'true' towing capacity as '(rated capacity - 1000 pounds) x 80%' Obviously, you should modify the 1000 pounds up or down based on how you load the truck. You might be able to up the 80% a bit if you will be pulling a hi-lo or popup or other tow with lower wind resistance.
To tow with an auto transmission, make sure you have a good transmission cooler and a transmission temperature guage.
When looking at a trailer to fit within your tow weight, don't be mislead by 'dry weight', which does not include any changes made after it left the factory, and it's not usable 'empty' any way. GVWR of the trailer is a much safer measurement.