I agree.
But can you run lexan to replace stock glass in the SCCA Solo II C-Prepared class?
I think 63-65 Valiant sedan would be the best choice. Maybe even a 60-62 Valiant sedan. You are going to use the 60-62 suspension anyways.
But you have what you have. And a 65 Barracuda is cooler than a 60 Valiant. It might not matter much after it's gutted as much as a C-Prepared car can get.