I would have just re-built it the way it should have been... putting a v10 was quite overkill IMHO, why fuck with something that is already perfect. I guess I'm a bit bias'd on engine swaps, but I do love E30 M3's.... But in this case, they turned it into something not as worthy... My suggestion take the M3 badge's off and put an v10 sticker on it with some NOS decal.
.... seriously though the project started out good and I got excited for a second, but then when I saw the V10 and M3 in the same sentence........