Here is the video I mentioned above. He is one of the better shifters on YouTube. You will notice that he uses no clutch most of the time, but has to use it a couple of times. I myself, although in the minority, like to use the clutch all of the time.
It's not a Chevy but a fine example of an old Mack. It is kind of hard to find a good Chevy or GMC example of Twin Sticks: