I made this one a few years ago for my 312-8, I took apart the original, not difficult, it was rusted out, I copied the internal volume, pipe sizes, number of holes in the internal pipes (baffles) The only difference was, I fitted a 'stack' outlet, it is sooooo quiet. Stainless from the internet was used, I made 'hammerforms' to shape the ends and centre baffle, all 'tig' welded, and then I cut the outlet for the stack the wrong shape and made the mistake of filling the gaps with weld instead of fitting a 'patch' / 'doubler'. I can't remember what it cost, but the materials were not that expensive.
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