FWIW crane makes a stud rocker conversion for stock heads. its a 3/8 stud for the rockers that has 5/16 threads on bottom that will screw into the 5/16 hole where the pedestal rockers bolted down originally. it also comes with guide plates and is rather affordable.. under 100 bucks last time i checked. the only bad thing is your using a 5/16 bolt in the head. not very strong and poses a greater chance of breaking with stiffer valve springs etc etc. but i guess it couldnt be much weaker than the stock setup because it used the 5/16 bolt also.
a better alternative is to have the holes in the head drilled out and tapped into a 3/8 thread so you can run a conventional stud.