Put the transmission in top gear, and gently roll the truck forward to move the engine to the next set of valves that need adjusting. I use the "companion cylinder" method where I watch the valves halfway around the firing order from the cylinder I'm adjusting. The exhaust valve will be closing, and the intake will be opening when the other cylinder is at top dead center ready for adjustment. This is called "rocking". Here's the procedure:
#6 rocking, adjust #1
#2 rocking, adjust #5
#4 rocking, adjust #3
#1 rocking, adjust #6
#5 rocking, adjust #2
#3 rocking, adjust #4
This assures each cylinder is exactly at the top of the compression stroke, with the camshaft lobes on the base circle.
Jerry