The one in the first pictures has the bolts (4-40 socket heads, 3/32" Allen wrench) inside the tube, with access through those holes opposite. Beware of those holes, because invisible flames come out of them at about 2,000* F. and will burn the bejeebers out of you. The one in James' picture has the screws coming through the engine muffler lugs, and makes a whole lot more sense and a better installation.
I have one of those mufflers, just like the #1 picture. AFAIK, the G.21 .46, G.51 and ST .60bb all have the same exhaust bolt pattern. I was thinking about putting some sort of threaded insert into the muffler and make it so I could bolt through the engine, like James' version. Or, I could probably be persuaded to part with it, so make an offer by PM if you want...plus USPS at actual cost.

Steve
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