I, along with Jerry M. and several hundred other small block Chevrolet Stock Eliminator racers, have been using stamped steel rockers on 7000+ RPM Stockers since the late 1980s when rules regarding valve spring pressure and lobe duration were relaxed. Within the past couple of years, NHRA bowed to pressures from racers and manufacturers to permit the substitution of stud-mounted roller rockers. Over the course of time, I've sorted, literally, through bucketsful of used rockers looking for sets that bear the identical markings, I've mixed and matched rockers and pivot balls, I've used a die grinder to open the rocker arm slot to fit over 7/16" studs, I've routinely put 425# of open spring pressure on them and and generally violated most of the generally accepted common sense "rules of thumb" regarding valve train longevity. At this point, I can safely say that the total number of parts failures related to rocker arm/pivot ball failures that I've experienced could be counted on one hand.
Many years ago, cam grinders for our sport began to grind extra lift into camshafts to accommodate the issues of inherently inconsistent rocker ratios so, I'm positive that if I were to switch the rockers on my Stocker motor to rollers today, I'd have go go through the entire motor to reset the components for legal lift measurement as read off the retainer surface. It has been my experience that the weakest link in GM's stock valve train stability has typically been the studs, not the rockers. Big blocks and other engine-makes have not been so fortunate when it comes to valve train stability and it is my opinion that those are the racers who urged the liberalization of the rules to permit roller rockers.
The above statements should not be interpreted as an indication that i have any knowledge about the details of Jerry's engine program. Having said that, I've always known him to run legal motors so the fact that his Z28 twisted over 8000 using stamped steel rockers without major problems is merely a given.