I believe they sell replacement studs that you thread in.
Your "clatter was probably because the rocker arm nuts weren't tightened down enough. With hydraulic lifters you have to take out the slack plus a bit more. With the engine running and warmed up, you SLOWLY tighten down the rocker arm nut. (If it wasn't clattering, back of slowly until it starts). Note where the clatter stops. You continue to slowly tighten down until the engine starts to miss on that cylinder. Back off halfway to where the clatter stopped. This centers the hydraulic plunger in the tappet in the middle of its travel. You can take out the "slop" before firing up the engine the first time. The rocker arms shouldn't have ANY slop, but don't overtighten! When initially firing the engine up, I'd "chase" the obviously clattering rocker arms before getting into the "serious" adjustment. No sense having them banging away which isn't good for them. Just snug them up enough to get rid of the clatter at first.