I'm wanting to do a complete drain and flush of my cooling system, and I was wondering if there is a drain for the block? I can tell there is still coolant in there, so I wanted to get that old coolant out.

Part of the reason is I still had the old green style coolant in there, and I was going to change coolant type, so didn't want to mix colours of coolant.

 

Not sure about the 6.0 but if there is any drain plugs on the 5.3, I couldn't find them. I pulled the rad and water pump when I did ours, jacking up the back of the car got most of the coolant out of the block. With it still jacked up I ran the garden hose into each side of the block and flushed out the remainder of the coolant. After adding 50/50 pre mix, my tester shows the concentration still at 50% so there couldn't have been much water left in the block.