RCM Revo BL mount with a KB 10XL?

[suicideneil]

Not a chance. The standard diameter for motors is 36mm, but the KB45 is 45mm in diameter- it wont be able to mesh properly without hitting the tranny. You could use a reverse motor mount though- mount one motor plate on top of the other, with some spacers inbetween, sandwiching the spur. You will need to make a custom second mount though, or modify the 2nd one, since the kb45 uses 4mm screws and has a 30mm mounting pattern (normal motors use a 25mm pattern).