for full roller or partials the ratio is still the same....In either case in 1.6 ratios you will have to elongate the bottom of the pushrod hole

Jeg's and Summit both sell a tool designed for the job....

You Do Not need to open the hole for full or partial rockers unless you intend to install screw in studs with guide plates too...

For cams upto .450 lift and "normal" rpm use the stock studs will be fine...more than that either way I would recommend the screw in studs.........Doc