NWSL question

[twilight]

I've been wondering this for a while, so here goes it. How does one know what kind of gear box and motor to purchase from NWSL? I have been thinking of trying one on my next Bowser locomotive project (maybe a PRR N2s). Now to my knowledge all Bowser PRR frieght locos are a 29:1 gear ratio. I guess this is of importance in gear box selection, but I also figure that the size of the enclosure the gear box and the motor will live is important, too. And while I'm thinking of it, how does the gear box and motor attach to the frame?

Thanks, and look for to the input,

Mark