I have personally owned one of these trucks and to tell you how to time it is pretty simple. There is a black box located on the passenger side firewall remove it and there is a single wire (i think it is tan and black) unplug it and set your timing to top dead center with a timing light. As for the cylinder and distributor cap timing you can get that from your local auto parts store, I know that they have it because i work at auto zone they can definitely print you a copy free of charge.
It has a timing chain that should last the life of the engine.
It does not have a timing belt. It has a timing chain which is normally good for the life of the engine.
timing chain
Chain
It has a timing chain, NO BELT
It is recommended that you replace the timing Chang, on your Chevrolet Silverado pickup truck, at 60,000 miles. Many times the warranty is voided if the timing chain is not changed.
it has a timing chain. not a belt
No belt. It has chain and gears.
with a timing light on the hermonic balancer NEW ANSWER: The timing is not adjustable, it is controlled by the computer.
timing belt
The Chevrolet 4.3 liter V6 engine has a timing CHAIN
0 degrees