2DOF build.

Hello, I have been following along for a while and I am going to start my first build. I have been collecting parts and I think I am close to having everything.

So far I have the following:

• 2 Jazzy Electric motors (120rpm at 24)
• 2 480 watt power converters
• ARDUINO R3 with ElectroCookie
  
• 2 JiLegogo bts7960 Motor drivers
• flanged u-joint

I still need to pick up the Hall Effect Potentiometers and tie rods ends but am I missing anything else.
Where do I find the keyway arm to connect to the motor? Is that a DIY or is there somewhere I can find it with the keyway already cut into it? If it is a DIY what length would I want for this motor to ensure the appropriate torque?

Does mounting the motor at the front or back of the rig make a big difference?

Thanks.