The mid-high 14 second times of these performance cars is interesting. Some while back, I put together a 383 1972 Valiant 4 door. I used only the finest in used junk, a 60,000 mile 1965 383 2 bbl. engine, no internal mods at all beyond lapping in the valves. It was a good thing I pulled the heads to verify internal condition, as 1 exhaust valve had a nice "V" burnt into it. A used valve from another head fixed that.
This engine was rated at 9.2/1 compression, and 270 HP. I added a factory cast iron intake, and an untouched Holley 600 cfm vacuum secondary carb. Exhaust was 2", (not a typo), pipes to cheap mufflers off of the stock C body log manifolds. The trans was a 727 from a Newport with a stock converter, a home brewed shift kit, and 120,000 miles on it. An 8-3/4 Sure Grip rear with cruiser 2.76 gears rounded out the drive train. With worn out M/T 14" S/S tires out back, it ran 14.80's with no tuning, using only first and second gear. The car weighed 3,240#, and I'm over 200. Why a performance car didn't fare any better I don't know.