I am not quite sure what type of power transmission system you are referring to by "mount to a hub for a spindle type wheel". I think you may be looking for a motor that will transmit power to the wheel through gears?
All of the motors that we carry have chain sprockets or belt cogs on them for a chain and sprocket or belt and cog type of power transmission system.
When looking at photos of the Baja Wagons I notice that for a chain and sprocket power transmission system a motor mount could be welded onto the axle of the 4-link suspension model, or onto the swing arm of the swing-arm suspension model. Then a chain could be installed between the motor's sprocket and a sprocket that is attached to one of the wheels.
I may not have understood your question though so if you have any further questions please let me know.
What I think Jim is thinking about is the adapter shown at this adapter to fit a sprocket to a wheel hub. The adapter comes in two halves such that the adapter clamps tightly around the wheel's hub. I don't think that this adapter can handle a lot of torque since it is just a friction fit. But the legs of the adapter extend through the forks (thinking of a bicycle wheel) to which the sprocket (of any requisite size) bolts.
jIM lEE
I want to create an electric wagon for my fast-pitch daughter and want to start off with a wagon from Baja Wagons.
http://www.bajawagon.com/48wagons1.html
Do you have an electric kit that can mount to a hub for a spindle type wheel.
I see the axel type on your website that requires a sprocket and chain, but I'm not sure that would work with the Baja set-up.