By what definition? Horsepower? Torque? Both???
I'm sure we can all agree that the "Muscle Era" was generally 1968-1972, though we can sometimes paint that with a broader brush and say 1964-1974 because that will include the premiere GTO and Mustang, and run all the way to include the swan-song Challengers, Barracudas, Javelins and final year for big-block Camaros & Firebirds.

I thought the Buick GSX won the torque trophy with an advertised 510 lb-ft of torque.
Thought it was the '70 Chevelle with LS6 engine that got peak advertised horsepower at 450.

So, both Muscle Car era; both with top advertised numbers.

But then the debate will begin over actual numbers generated. Most will argue that the 426 Hemi actually generated North of 475 Horsepower and has been somewhat proven with "stock build" dyno runs.