Another component of this issue is the mechanical adherence to period specs. With Formula Junior for example, there is a philosophy supported by an ever increasing rule book that subscribes to the "as it was, so it shall be" approach.
The intent is to have all mechanical components of the cars as they were in period (1958 - 1963). However despite the intent and the rule book, performance from engines has spectacularly improved. Period works engines that put out around 100 bhp at about 8000 rpm are today approaching 130 bhp at 10500 rpm. How much of this is down to improvements in such things as metallurgy (should you be able to use titanium parts when they weren't used in period?) and how much is the bending or "interpretation" of rules?
How do you question, say, potentially dubious head modifications made today when all the period heads have long disappeared?
Would a 30% improvement in performance from a engine be expected using the same period components - could these gains be down to improvement in such things as head flow technology etc?