I have a 1969 Chevelle SS 396 L78. I am looking for aluminumized head pipes & tail pipes that are oem 2 1/2" ID. Where can I purchase these? It's important that they are aluminumized.

Gardner Exhaust sells a faithful reproduction of exhaust systems. I believe they have a website. For what it's worth, I think the tailpipes are 2 1/4".

If you're looking for 100% factory look and fit , go with Gardner exhaust. I talked with them over the phone, they make only exact reproducions of factory exhaust systems.
They even have Chambered exhaust, which was an option for 69 Chevelles and camaros.
Check out their website, they even have sound clips of some of thier systems.
Http://www.gardnerexhaust.com

Jeff