[Dwight Southerland]

oldskool - My observations that may give insight into your questions.

1) Valve spring pressure and not camshaft duration is the major factor in the skyrocketed cost of stocker valve trains. The reason we have such radical camshafts is the result of being able to have the valve spring pressure to accomodate the increased rates of lift and elevated engine RPM.
2) Likely the cost of enforcing camshaft specs and valve spring pressure is the reason NHRA elected to change the rules. It takes a lot of time for education of technical staff, cost for maintaining the staff and increased office support to insure that consistency is adhered to in the field for checking camshafts for duration and overlap. The number of stories of questionable certification procedures from back when they did check duration and overlap would be an indication of how difficult it is to maintain the procedures. Also, there are many political and technical issues behind keeping that process in place that are not easily solved. 'Not easy' means money and time. For NHRA to continue the Stock eliminator, it is much easier with fewer cost implications to do lift and that is all.
3) IMHO a limit of valve spring pressure would lessen the cost of engine building in many areas and I wish they would do that. Checking valve spring pressure is not that difficult in the field. Certainly no more difficult than checking camshaft lift.
4) Standard lifters run into questionable reliability over 130 lbs on the seat and about 350 lbs over the nose. You can do more than that successfully, but you need to follow some definite processes. The NASCAR community ran flat tappet cams for years without the benefit of tool steel or ceramic lifters and there is a boat load of information about how to maximize use.
5) Depending on the combination you race, the super expensive valve train is not necessary to be competitive. Most common 283, 327 and 350 SBC combinations do because the development of the technology from so many racers has pushed the standard of performance to a level that requires those parts. BBC solid lifter engines are the same.
6) It is not the duration that makes the requirement of the tool steel or composite lifters, it is the rate of lift and the valve spring pressure. And you need the valve spring pressure to operate in high RPM ranges. We used to run 260-275 degrees duration back in the days of stock valve spring specs on certain engines, but the rates of lift of the camshafts were much milder and we didn't run the RPM levels that are common today. At 6000 RPM on your Pontiac engine, you could be judicious with valve train weight and get by with valve springs that would not require tool steel or ceramic lifters if you don't get nuts with rates of lift on the camshaft.

More for you to think about and get a clearer perspective.