If you are still having issues with the exhaust you can buy header flanges from GM (or others). Next check out all of the choices of headers for 5.0 ford motors...after you make your selection, cut the header flange from the ford re-route the front tube and weld the GM flanges on. With the exception of the front tube on each side needing some tweaking the exhaust port spacing is the same. Ford headers are cheap too. Go to NAPA and compare header gaskets for each engine.....you will be surprised how close the match.