as tt pointed out select the best looking less worn rockers,if any look a bit sus find new ones,these parts have a great deal of pressure on them at any revs and any signs of rust or pitting or hard face wearing off and they shouldnt be used on your brand new cam,,idealy the rockers should all be replaced with the new cam,,no one would ever run worn lifters or visa versa on say a small block new cam,you can get away with it a little more on these engines though,little being the operative word,sure plenty will chime in and say how they have mixed and matched these parts,so have i,but for a new cam i myself would run new or rebuilt rockers(hard face welded and reground)