'64 Barracuda Exhaust Help

I am looking to put a 2.5" dual exhaust on, from the manifold back. The car already has dual exhaust because it has a 318 in it. I am going to modify the trans member to better accept the dual exhaust. Wondering from everyone's experience, how much louder is the exhaust sound inside the car if I dump the pipes before the axle vs. running them out the back? Also, what type of mufflers would you guys recommend for a nice sound, but not too loud? Anybody have some nice mufflers they want to sell? :-) Thanks in advance for everyone's help, greatly appreciated!