What’s involved in swapping out the Rapido Couplers on a Walthers N scale box car to have magnetic couplers like my Kato trains? Would I have to completely replace the trucks?
Are the couplers on Kato trains what they call MTL or Magnematic?
The easiest way, in my opinion, would be to slice the existing couplers from the trucks, at the flat portion where the spring ends near the pin holding the truck in place.
The best way to do this is to remove the trucks from the car and use a utility knife to slice-off the unwanted portion.
You could then replace the couplers with body-mounted Kadees. See the Kadee website for the appropriate couplers to use.
You may need to adjust the height of either the couplers or the car itself in order to get reliable performance, but it’s not difficult to do.