Post or Non-Post Cars?
Welcome to FABO, Kyle. You should have fun here!
The previous comments are all correct. The post cars are lighter and the body structure is more rigid due to the sedan post structure which makes them better for racing. You'll also be able to build a better 'sleeper' out of a post car: drab paint, wide steelies, no 'flash'.
But hardtops have the better 'musclecar' look, especially when cruising with all the windows down. My personal taste is for the hardtop - that's what my current '69 Dart build is based on.
It's all about personal taste, and at 15 your brother will probably be happy with anything with 4 wheels that runs. I agree with you, make sure he's happy with what he's going to have for the future and won't want to do something else in another year.
