Do u want stock appearing or actual headers?
Headers are easier! Lots of talented header builders out there, and don't forget hospital handrail fab companies, aerospace and food service plumbers/ welders. Here in Phx,AZ. We have many aerospace welders versed in heliarc welding exotic metals, so stainless is a piece of cake for them. Google the companies, sit in the parking lot, and wait for shift change and ask if anyone is looking for side work.
Custom water jet or plasma cutter companies can make you flanges based off of gaskets, just make sure they add metal area around the outside of the ports for strength and sealing. Stainless u bends in different radii and thickness are easily obtainable, and look at the vendors of 86/87 headers to see what thickness flanges and tubing they are using.
Most sidejob guys will do the job, IF you bring them the flanges, u bends, the original headers, and LOTS of pics of the old ones installed on the engine, so they know what routing to use. Also pics of 86/7 headers, so they have an idea of what is good.
Most header or side job guys will and can do the job, they just won't want to waste time finding the materials, and having the flanges made.
Google is your friend!
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