Hello Perry, in the old days an alternative to buying pricey aftermarket cast iron exhaust headers for a six-cylinder inline engine was to take a cutting torch and burn a hole in one end of the stock exhaust manifold, weld on a new outlet utilizing a flange cabbaged from something else, then a blocking plate would be welded in somewhere within the manifold to redirect half of the exhaust gas to that new outlet (sorry, but I don't know that much about it). The resulting racket was something different than that produced by headers and from what I heard growing up, Chevys for some reason had their unique sound. As much as anything, it was a way for kids with little $$$ to get around pricey speed shop equipment.