The oil change book at all the parts stores and the Chevy dealers say 5qts. I have always used 5qts. I think since the oil filter is high up on the fender well it always drains back into the crankcase when the engine is not running, so it shows a little over full when you check it.
I use Amsoil 10/30 and change it every 10 thousand miles.

 

thats a godly motor there =P