I am in the process of upgrading my 5.7l log exhaust manifold into tge srt8 6.1l manifold for improved performance. I purchased the manifolds and need only the midpipe flanges to finish building my exhaust system. My preference is to use the oem srt8 dp flanges to get the best sealing properties possible. Anybody has a set willing to sell?? I can also have the flanges custom made but I do not know what material to make it out of to avoid any thermal expansion leakages when the manifolds heat up. Anyone knows what material is the manifold flange made of (mild stainless steel, hardened stainless steel, ......etc)??