I would strongly suggest buying headers that fit vs. hoping that you’ll save money getting an exhaust shop to make them fit. There’s a hood chance you’ll end up breaking even cost-wise, and you’ll definitely have a worse final product.

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2011 M3
2006 Sierra 2500HD 4WD LBZ/Allison
2004 X5 3.0i 6MT
1995 M3 S50B32
1990 325is
1989 M3 S54B32

Hers:
1989 325iX
1996 911 Turbo