Hughes Rocker Shaft Shims Installation Vid
It takes a bunch of time to get the side clearances right. If you do not use a feeler gage between the two sides when tightening the rocker hold down it will shift and throw off your clearances. I found that roughing in the whole rocker shaft stack on the bench then making fine adjustments to the one of two big hold downs after the 5 shaft hold downs are tightened, do one at a time, works pretty well. I just ground down the sides of the big hold down I was trying to get right, doing one side at a time. Use a caliper to know how much you need to remove.