Before you jump to conclusions of a bad head gasket, why don't you get a cooling system pressure tester and pressure the system to 15psi and then check for drips. A small coolant leak, or pinhole in a hose, overflow tank etc. can spray a couple feet easy. You have an EGR cooler on that side and also heater hose connections as well as the overflow tank and hoses. As far as the head gasket goes, start the truck and let it run for a few minutes and feel the upper radiator hose. You may feel bubbling inside of it which would be an indicator of a bad head gasket etc. Also when a head gasket goes bad you may see white smoke from the exhaust on start up, or while driving, and also the temp. gauge tends to fluctuate alot while driving.
2006 K3500 Silverado, LBZ, 243K miles Raptor 150GPH lift pump and fuel lines, PPE race plug, Magnaflow cat-delete 4in exhaust, 42% over Industrial Inj.CP3, Rebuilt Injectors 30% over, 4094VVT stage 2 turbo, autometer gauges, EGR block off, EFI live tuned by Idaho Rob, Banks cold air intake, Banks super scoop