That was my point Edbert. Hard to imagine anything with 350cfm of flow and 2.80 gears could crack the 15s, much less 14.6.
While the cars had bad tires in those days, a stock 289 C4 with 2.80 gears wouldn't need any better tires anyway. I had a 66 Comet Cyclone GT with a 390 and sometimes it would hook up, and sometimes it wouldn't. I was running highway gears as well.