You guys are way ahead of me, however, I'm trying to catch up. As Mario says, "The learning curve is steep." That said, my first experience with Mario's Shapeways offerings was with an Atlas O RS, this past summer, and I was extremely impressed. The installation was easy and flawless.
Then I took a leap of faith and tried Mario's Lionel GP30 mounts on my Milwaukee Road MTH GP30 and, not surprisingly, they worked flawlessly, even matching up with the pre-drilled holes.
Since I always order one extra (just because I know I'll wreck one), I tried the spare on my MTH NW2 and it fit perfectly, too, protruding just enough beyond the carbody to give the illusion of prototype:
Now, if MTH would just come out with their Premier GP30 in CGW...