Is a motor swap an option? For all that money I feel like you can source a NA motor that will make comparable power. S62/S85, LS3?

If I had extra cash I would definitely do an S62/S85 swap E53. Alpine White 3.0i with added iS fender flares, style 87s, etc

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2004 BMW M3 Individual
2009 BMW E70 X5 35d
2011 BMW E70 X5 35d - Totaled
2009 BMW M3 E90 - SOLD
2006 E53 X5 4.8iS - SOLD
2002 E46 M3 Convertible - SOLD
2006 E46 M3 ZCP - SOLD
2011 E70 X5 35d - SOLD
2000 E39 ///M5 - SOLD
2003 E53 X5 4.6iS - SOLD
2006 E83 X3 3.0i MSport - SOLD
2000 E46 323Ci - SOLD