Forget that 40 yr. od GM chart
Use the new, better, correct method describe above on the valves opening and closing . This works well on 1.5 ratio rockers, I use 1/10 to 1/3 turn preload (depending on iron or aluminum heads) on 1.6 or higher ration rockers on hydraulic lifters
You can also use the piston at top dead center method on the firing stroke also

Another thing to consider is the adjuster diameter and thread count, the 3/8x24 adjusters have .042 adjuster movement for one full turn, the 7/16x20 adjusters have .050 per thread movement 1/2 turn on the 3/8 adjusters is .022 preload, 1/2 turn on the 7/16 is .025
the devils is in the details