I called up Dave at Spintech and said "Listen, I need a 3" exhaust for a 68 Camaro. I want an X-Pipe, I have 3.5" collectors, I want oval tubing, and I have Air Ride, but I want full tailpipes. Oh, and I have no idea what parts I need to buy."
He responded by slowly rattling off every part number and quantity we would need and then putting together an order. I suggest you do the same. Be sure to say that Steve at Twist Machine referred you so that you get the same treatment. He was very patient and thorough. Note that this is for a full custom system. There is no such thing as an off the shelf oval system. Dr. Gas is a great bunch of people as well. And they are the originators of the X-pipe.
http://www.spintechmufflers.com/spin...ntechindex.asp