I just finished up the exhaust on my '40. It's 2" tube, without mufflers with Fenton headers up front. The engine is a 284 with a Winfield SU-1A cam. The car may sound a little loud on the outside, but it's actually quiet inside since the exhaust runs all the way to the tailpan:
http://youtu.be/KHPjxj-JZXo