Just tried to install some Comp Cam 1242-16 stock type rockers on my 330 Olds with no. 2 heads and they won't fit. The holes in the pivots are too small to go over the studs on the heads. Are the studs normally 5/16? These appear to be 3/8. Are later model 350 rocker arm studs 5/16? Can these studs just be unscrewed and replaced with the correct diameter ones to make these Comp rockers work? My stock rockers show wear on the part that contacts the valve stem and the push rod pocket area too. I don't want to re use them.