Need info on Supertrapp headers for 550-650-750

Bought a NOS Supertrapp header off ebay for my 750E. It's the same part as the 650 uses from what I've been told. Need a midpipe and muffler now and there is a NOS Supertrapp from a '84 550 on ebay that I've got my eye on. My header has a 2.5" exit. Does anyone know what size the 550 supertrapp muffler and mid pipe is? I know it won't be a direct bolt on, but I can mod it to fit if the diameter is the same.

BTW, I sent the seller a message but they don't answer inquiries about items because they claim to have too many.

Thanks