Hi Mike, and welcome to the site.
You should not have any problems flat towing your truck, but you do need to put the Transfer case into neutral position. There is an option from the dealer to add a button that switches the transfercase into the neutral position. It costs about $50.00. There is another way and that is to take the transfercase motor off and physically move the gear to the neutral position, but I would just pay up and not worry about having to take anything off or on.