Kind of had you in mind when I posted, roo.
Group 7 was never meant to be regulations to build a car to.
Sports cars were 'grouped' according to engine capacity and weight.
Group 7 was just for cars that didn't comply to any other group, hence no weight limits or capacity limits.
Sure, they were heavier than F1 cars (530kg - 690kg) but McLaren had 8.3 litres - F1's 3 litres.
I love the mindset of the drivers at the time:
It was largely Flegl who created the Porsche 917-30, whose 1100 horsepower, the SCCA bitched, was killing the Can-Am series. Donohue disagreed. “We’re far from having too much horsepower,” he asserted. “My definition of too much horsepower is when all four wheels are spinning in every gear.”
I also have the whole 1971 Watkins Glen race.
I'll upload it if anyone wants it but be warned, there's no DRS so overtaking is low.
(they've even left in some motorsport related ads of the time