I believe Car & Driver did a road test on a pre-production 383 Barracuda in August/September 1966, but this wasn't available to the public yet. Also, most all pre-production cars ended up being crushed.
If any of the modifications that they make when making the prototype test cars cause a structural weakness and the public buys one of those and gets in an accident, the manufacturer can be held responsible and sued... So ALL prototype pre production cars are scrapped after they are done with their testing...