I purchased a undec Red Caboose GP9 with the stock drive in it. It uses a Pittman motor with flywheels and the old Atlas/Roco trucks. I placed it on the track straight out of the box and it ran surprisingly well. It no couplers installed so I attached it to six All Nation freight cars with a piece of wire. It pulled them with no problem.
I had planned to install a new frame with some Weaver drive components that I have but I think I may leave it stock. I believe it will do fine on my meager 12 x 16 layout. Now I have the detail and paint it. Trying to decide on Columbus & Greenville or Illinois Central green diamond scheme. The C&G locos were actually GP7’s so I more than likely go with the IC.