Knowing these people, I'd say that if they could get that much, they certainly would, need it or no. The same applies to the various sprint cars which are very similar in their construction except for some of the armouring. There are various videos on YT that show exactly what I mean, no doubt including tonight's BriSCA F1 World Championship taking place at Kings Lynn as I type.

Engines are unrestricted on capacity, so the all iron 427ci / 7 litre was the entry point to big block Chevys, not what everyone had - 454s were already very common. Less than a decade after this was filmed, standard production blocks were mandated to control costs - some of the top drivers were running totally aftermarket alloy engines over 500 cubic inches on tarmac by that point. Your guess is as good as mine as to what the most powerful engine was in the late 80s, but it certainly wasn't an all iron 427 with 400bhp.