I can say without a doubt the 70 Superbird would win.

Not because modern technology hasn't improved cars potential but the 70 Superbird was too fast and they throttled down the engine displacement after 70. It was the last year of unrestrained power in my opinion.

Nascar has always tried to slow the cars down when they approached 200. Now its closer to 180 for safety.

It used to be the leader would be 2 or 3 laps ahead of some close competitors. The power let them run away with races.

Now they are all so evenly powered the leaders are almost always a few seconds apart. They just can't outrun the competition anymore.
Races were once won because of the car. Now its 75% luck and 25% driver.