Honestly, most of the street races I was around in the mid to late 70s and early 80, if you had a mid to low 13 second car on the street, you would win more than lose. My buddy's 70 Roadrunner, Purple Stripe cam and springs, specs were the one down from the .509, I think .488 lift/284 duration? dual plane aluminum intake w/780 CFM Holley 4bbl and headers. He went from the 3.91 ring and pinion gears to 4.3X in his 8¾ Sure Grip, and a Pistol Grip 4 speed. Centerline wheels and some pretty wide radials. 1st gear was a lot of noise and some forward motion, but if the car he was racing hadn't gapped him yet, 2nd and 3rd were game changers because his Roadrunner was a rocket.
Still, only a 13.XX second car, but most of the races he picked up were high 13s, and even more 14-15 second cars.
There were some solid 12 second cars out on "the scene" but they were known, and even the occasional 11 second car, but those were like unicorns.
