Yeah, muscle cars were good in the "go" department, not so much in the "stop" department!
I have a '67 Impale 327. Not really a "muscle car," but a perfect example of '60s engineering. I remember the first time I took the car for a test drive and tried to stop. I thought the brakes were broken!
I rebuilt a 350 Rocket for my '72 Cutlass , going 30 over with oversized iron pistons . I played a bit more with the exhaust / mufflers by going with a larger diameter system , boosted the electronics , etc . Nothing major there . Problem being , no consideration towards the braking system with the added horsepower and speed !
There were a few times at the onset where I actually believed that I would have to Flintstone it ! Lol !