03 H2 with 6.0 liter vortec slow to start
 

Almost every time I turn the key, it takes 3 to five seconds to start. I have also had gas smell on a few tries. Once started, it will act like it is missing and then run fine. 66,000 miles. Anyone seen ths before? Where should I start looking?

It might be running rich. maybe a leaking injector. When you start your truck and let it warm up then turn it off and then start it does it still take long?? Or does it take long when you leave it overnight?

Check the fuel pressure regulator on the driver side of the engine. It is a round little valve stuck onto the side of the fuel rail with a vacuum line going to it. Pull off the vacuum line. Turn the key on, but do not crank the engine. Then off. Then on again (still not cranking, just cycling the key). Now go look at the regulator nipple where the hose was. If you see gas, it's bad. Injectors aren't real common on these motors, but regulators are. hth.