RE: Challenger in NASCAR
You forgot to mention that Ford also rolled the rocker panels, which made it easlier for the race teams to "lower the body" on the frame.
If you look at the record book you will find that the Aero Fords and Mercurys win more races than the Wingcars......but the Wingcars left an impression on all those who raced against them (and the fans for that matter)
Bottomline...the fastback Ford/Mercury was a better starting point for a racer than the 68/69 Charger.
And, if anyone thinks that the Daytona and Superbird were not Aerodynamic....one look at how well the #22 Daytona was running in the 1971 Daytona 500 (before being taken out in an accident)..with a 305 vs the field of stock bodies running big blocks proves how important aero is at high speed.
Also, look at the records set by #71 Daytona team at the Salt flats and how long the records stood.