One word- - - - -DON'T! I used flex pipe to do the same thing on a 58 Chevy many years ago, and found out that flex pipe vibrates, and breaks at the end connections, repeatedly! I could count on cutting the pipe back and re-connecting it about every 500 miles, and it would get too short to reach very quickly. It's not worth the effort, and a custom-bent real pipe from a muffler shop doesn't cost that much!
Jerry
