Honestly I am not aware of any dealers for Stahl. Due to the fact that they custom build headers as well. Thats not to say there isnt dealers; Im just not aware of any. If I were a header company I would want the end user dealing directly with me to make sure the header fit the application and setup due to so many options and combinations. Most people do not realize just how complicated headers can become with other aftermarket parts and components. If you have aftermarket heads, mid plates and/or running a non conventional transmission then usually dealing with a company that is willing to build a header or knows their headers will work with certain components then that is your best bet to reduce the frustration factor. I have built a few custom headers and I applaud the guys that have this ability cause I have seen some headers that are pure works of art. Not to mention the fact that they also produce horsepower.
I personally would only run stainless if I were buying headers if I was planning on keeping the car for a long period of time. They will last a very long time. Only thing that really fatigues on stainless are the welded areas but that is usually on headers that are supporting a turbo. Most other applications they will last longer than the engine. lol
What is your overall expectations with the car? What do you want to ultimately do with it? Street/strip or pure strip?