Hey Steve, Tim is right. You have a good opportunity to make on of the best mods on your car to keep up with that 427. You should send your pipes to Rob Camp at Keith Craft. He will change out the exhaust to a much better free flowing one (for a serious gain in horsepower) and even re-coat your pipes like you are wanting to do, all at the same time. Here is one of his posts from a recent exhaust thread:
"I have built several side pipes for SPF and Lone Star cobra's using the Howe Muffler and merge collectors and have consistantly picked up 12% increase in rwh over stock SPF pipes. I have done it on cars with 350 RWH to 508 RWH and we also turn the tips down 15 degrees to make the noise go downward and make the noise more tolerable. We have a special of $995.00 plus shipping to take your stock side pipes and install the merge collector, muffler and tips and re-coat the pipes. I can be contacted at 972-578-3550
thanks"
Rob Camp
Keith Craft Motorsports
Managing Partner
From what I have read, you will probably have to re-jet your carb after the exhaust modification is done. Here is the thread where the above info comes from:
http://www.clubcobra.com/forums/showthread.php?t=74401
Hope this helps.