There is more than one way to clean those rusty drive wheels.
I would be hesitant to use a wire wheel because the motor truck has magnetraction.
I would also be hesitant to run the engine upside down to clean the wheels because I'd be concerned about the dust getting all over everything and into the bearings.
Without seeing good pictures, it's hard to make an alternate suggestion on cleaning.
I think I would be most likely to:
- remove the truck assembly from the engine.
- remove to truck sides from the truck block if possible.
- use fine sanding cloth moistened with oil to polish away the rust by hand.
I have rolls of 220 and 320 grit sanding cloth for just this sort of job. The 220 roll is 1 inch wide, and the 320 roll is 2 inches wide. Often I split pieces lengthwise to get narrower strips. If the rust was heavy, I'd start with the 220 grit and finish with the 320 grit. If the rust was light, I would go with the 320 grit from the start.
I like to move to a clean part of the cloth very often.
I guess wet/dry sandpaper could be used as well, but I prefer the cloth.
