U-67's. My all time favorite overhead mic next to a pair of C-12's.
Yes they will work great. I have used them in a 3 mic technique or more typical spaced overheads. I would use the roll off and probably the pad and they may need a little more eq than some other mics but they will be beautiful. Unless you room has any kind of boxy issues (which if your using the UM-900's you would have found by now since they are also a great mic) you will love how they take eq and the clarity that you can get if you have a good pair of them.
The studio I worked at 8 years ago bought a pair of quite nice ones and I would run them through either the Focusrite Red 4cnl pre or a pair of Neve 1073's.
Now the studio is going downhill and the U-67's never work and they won't send the golden jems into get them fixed
With your pre selection I would choose the SCA but I haven't heard the Mercury. If they are anything like a real V-72 they might be a bit creamy but will probably sound amazing with lots of bottom end (Sometimes good sometimes not. Just depends on your style and preference.)
Give it a go and let me know what you think of them,
Michael Greene