If the "Dual Gauge" trucks date from the WW2 era
they would be like the ones we shipped to the RR Battallions during that time. The axle wheel seats
were machined so that wheels pressed on to meter gauge could be pressed a little farther on the axle to 36" gauge. This required dismantling the trucks and use of a wheel press which I understand the RR Battalions had as part of their equipment.
If my memory serves me right the brake beams were designed so that they also could be adapted to the new gauge. Brake beams I remember well because as a checker I had to make sure that there were equal numbers of left hand and right hand beams in the crates. Something that is not a problem in the brake arrangement of standard gauge cars.