Adding Kadee’s Is not a problem if the mounts are in place. Taking apart the MTH trucks can be tedious. Some simply use cutters to remove the coupler. Then there’s no turning back if you decide to change back.
My suggestion. Buy a couple of Weaver hoppers that will fit your scheme with diecast trucks. Easiest conversion you will ever do. One screw removes removes the truck and coupler. Leave the coupler off and mount the truck. Shim accordingly with washers so that there’s no wheel rub on the underside. The mounts are present to add the Kadee’s. I wouldn’t even bother with a height gauge for the time being. If you don’t like it. Your only investment was the 2 cars and couplers and you can easily go back. If your retaining your coil couplers. The Kadee 805’s mate better with the 3 rail coupler. Most MTH coil couplers don’t play well with Kadee’s. Lionel and Atlas are fine.
