they also may used the wrong push rods, I would check that too, that would create a hell of a bind and breakage if they're too long
also high lift cam Pontiacs used a higher valve cover gasket to clear the higher lift, Ames performance has it, I use it with my 068 cam just because it makes a better seal, it also requires taller bolts
this person may not have rotated the engine when they set each rocker nut to 20ft lbs, if they even did that, it's possible that is what caused the breakage and other issues, if the nuts were screwed down too far it would hold the valves open or one or two and break things
