I did it, just remove the 4 screws on the bottom of the truck, lift off the plate that covers the gear, while holding the truck upside down so the wheels don't fall out then you can slide the coupler assembly out (up towards you), screw the plate back on again. On the front of the frame I drilled two 2mm holes and mounted an 805 Kadee coupler with two 2mm screws. On the rear end of the frame I did the same but mounted a Kadee 806 (shorter version) because of available space. Adjust the height of the couplers with necessary shims.
Good luck,
renrew in Switzerland
P.S. Before I did the above modification I took the whole truck apart, cleaned out the old grease and put fresh grease on the gears.