Look at the 1st pix in post #10. See the curved flat metal pieces under the rocker shaft bolts, that curve around the shafts? Those are the spacers and go between rocker pairs as shown. There are 5 of these on each side, 3 narrow and 2 wide. The 3 narrow ones go in the middle and at each end.
These are not like the ring spacers in the adjustable setups. The rocker pairs have no spacer between them like shown.
The pushrods are different like you probably already know.
There are square notches on one end of each shaft; these go down and to the left as you face each side of the engine.
BTW, the bolt torque needs to be 15-18 ft lbs; many service manuals list it higher which will result in broken bolts.