Obviously
I knew a guy, that came to the drag strip my dad worked at, one of the area Mopar guys (guys that
every vehicle they owned was a Chrysler product), he had a beautiful '68.
It was an all-black (he called it "triple black" - black inside, outside, and black-tinted windows) GTS that was a factory 340 car. Looked (and was) stock-ish.
Slicks that fit in the wheel wells, aftermarket wheels, no visible exhaust, and a six-pack style hood were the only obvious visual cues on the outside, bucket seats and a B & M Pro Stick on the inside. Looked more or less like your average mild street hot-rod.
Under the hood though....a very much not-stock 440 six-pack from a '69 Roadrunner, built to go
really fast on the drag strip, and be drivable-ish on the street. Only major body surgery was what had been removed in the engine bay to fit the full-length headers.
Even on those narrow slicks, it'd pull the front wheels about a foot off the ground at the drag strip.
Iirc, would run low 7s? on the 1/8 mile track.
Then he'd go home & put on street tires, bolt mufflers to the ends of the headers, and go driving around in it.

It looked a lot like this one:
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