4.8 mufflers won't bolt onto a 4.6. The flanges are different and "clocked" differently. Others habe done it, but it requires cutting off the flanges and adapting.

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2012 xDrive35d
2001 BMW X5 3.0i 5MT
and two 1987 Corvettes - Callaway Twin Turbo and Guldstrand Grand Sport 80
Block Tester