This car was on display at the Plymouth Fall Festival here where we live in Plymouth, MI (interesting coincidence isn't it).
Aside from being yellow, the car reminds me of the family car we had when I was in grade school. If I remember correctly it was almost the same model except for a few optional accessories.
This car has the 440 c.i. engine like ours did, but we had blue paint with an upgraded wheel package and blue vinyl seats. If I recall correctly the back rally stripe was on the bottom of our 1968 Plymouth GTX. It had a four barrel carb, 3-speed automatic on the console, and Dana posi-trac rear end pushing somewhere in the vicinity of 430 hp. Stock!
If my dad still had that car today, it would probably be worth somewhere in the vicinity of $25,000 - $30,000 easy.
I believe there were only about 1,100 of them produced in 1968 (just enough to meet the NASCAR requirements). This was a true ready-to-race factory race car capably of 150 mph + in stock condition.