Here's a link to pics of my buildup so far. It uses an Atlas U23B drive and you have to machine the frame.
http://public.fotki.com/dieseldetailer/ho-diesel-projects/alco-c430/
You can use a Kadee plastic coupler box that comes with the couplers. Drill the coupler pad on the Athearn with a #50 Drill bit and tap it with a 2-56 tap. Install the coupler box with a 2-56 screw. If the coupler is too low you can file the bottom of the coupler pad down to get the correct...