Wouldn't you buy the same size muffler as the pipe then use an expander to fit the pipe snug over the muffler? at least thats how I would do it or how a shop would probably do it if you took it to them.

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2003 Ford Ranger XLT 3.0L Flexfuel V6

Underdrive crank pulley
15x8 Procomp Xtreme Alloy 7069
31x10.5x15 Dick Cepek Radial FC II
Cherry Bomb Extreme