The M5 block is the same block and should bolt right up to the stock tranny. I believe the tranning can handle the HP so that should not be a problem. I think the big headaches would be retrofitting the ECU and wireharnesses and all the other supportive hardware. While it sounds like a really cool Idea...for the same money you do a Dinan S3 and probably have a faster vehicle and one that is more desirable are resale time.

__________________
pepatrick
2002 X5 4.6is
oO ( )( ) Oo
o ===== o