When looking at the work required to make a later N62 4.8 work in the X5, I can't help but wonder if it would be easier to put N62B44 heads on an N62B48 block.

Some further info:
https://www.bimmerforums.com/forum/s...-swap-question

Basically, you need an intake X5 N62 donor to make this work. Whether your current one is usable, or you buy a 4.4 to combine.

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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