Having looked at MRS1 trucks in detail for this feature, the trucks are made so there is room therein for wide (and narrow) guages. Reguaging is accomplished by transferring the traction motors to a set of wheels which have the desired guage and then moving the brake levers to whichever set of holes in the truck frames is appropriate so the shoes line up with the wheel treads. US locomotive wheels are pressed on with 120+ tons of force, and as such can't be slid around on the axles at will. They must be pressed off and a new set mounted to the desired location(s). If you look at any Little Joe (MILW and CSSB), there is the same extra width in the truck frames necessary to accommodate the Russian and Paulista guages.