'40 Olds convert sounds to cool, show us some pics. Re. the dual exhausts, don't think you'll ever find a vintage dual set up, talk about hens teeth. Two options. Have tube headers made, the hot rod guys do this all the time, or have a REALLY GOOD welder split the stock exhaust manifold. I'm lucky with a local guy that's been welding cast iron and doing split manifolds probably for the last 50 years. You need to check around your area in hopes of finding the guy that really knows his craft to do your split manifold. Also you might run this question past the guys over at
www.inliners.org or also H.A.M.B. website.
Best of luck
