There is the bottom (6 o'clock) hole with or without the banana groove plus the hole you will be drilling at 3 o'clock thru the rocker & shaft on the valve tip side and on the opposite (9 o'clock) pushrod side, the hole you will drill into the shaft past the already there hole in the rocker for a total of (3) holes. with the pushrod length corrected as needed either by adj pushrods or different pushrods & each pair of in/ex lobes on base circle (TDC compression for that cyl) & the rockers adjusted side to side with the proper addition of shims and slight spacing of the 5 holddowns so that everything is mocked up dead on & adjusters to zero pushrod clearance THEN with your holes already previously drilled in the rockers, scribe thru those 3 & 9 o'clock holes to make a circular mark(s) on the dykem on the shaft for where to drill. You will need to drive out then replace with new, the end plugs so you can deburr the ID of the shaft.