This would be my approach. From my limited experience the road BB5 and BB7 were shipped for use with 140mm rotors. For 160mm rotors the caliper needs to be tilted away from the rotor by extending the length of the front post - which you can see on your old mtb caliber adaptor. The new one looks like it will only work on a 140mm rotor, even though it was apparently shipped with a 160mm rotor. Just a guess. i bought a (post mount in my case) adaptor kit instead of fiddling with washers and spacers, which has the correct interface for the adjustment washers to seat correctly. As was asked before, why BB5 and not BB7, which are tougher, more precise, both pads are adjustable and uses larger pads, which would possibly not necessitate using such large rotors.