Adjustable rockers

You want to make sure what kind of lifters you have. There are standard ones, and there are ones that require very little preload. If the catalog says "must use adjustable valve train" for your lifter part number, then you don't go that far.
The basic deal is, you thread the adjuster in until there is 1 thread showing below the rocker arm body. Then you measure for you pushrod. Once you have the right length pushrods, you then watch the plunger inside the lifter and slowly thread the adjuster screw down until there is either about .010" preload if you have the performance type lifters, OR .040" preload is you have factory type lifters. This works for any hydraulic lifter, including a roller.