MTH 3 to 2 Rail Conversion

I do not have the part numbers but can offer this advice. I would try to return or sell the engine you have and then purchase the 2 rail version. MTH usually does not sell the parts you would need to convert it based on my experience. If this is a 3-2 engine, then you can purchase a conversion kit for the wheels. As for the pilot and hand rails, you're on your own most likely. Some on here have converted a MTH 3 rail and I'm sure they will chime in but as I said, I would just try to find the 2 rail version and be done with it.

I am in the process of converting all mine to the fixed pilot, full length rails versions, although for 3RS... it is worth it. I've been able to make a pilot filler, make new handrails, and a pattern I use for drilling holes in the pilot to line up with the holes in the body to secure the pilot. There are small holes for the kadee couplers you can also use with a #2 sheet metal screw.

take a look. I also made a cover plate that goes around the draft box to cover any unwanted "holes" where the 3-rail coupler went. The handrails are .025 brass wire from Tichy Train Group that I formed using another 2-rail loco I own as a guide. These look great compared to the 3-rail versions....

The gap is 4mm between the bottom of the frame to the top of the pilot. (distance between each step on pilot)

It does take time to do, but worth it. I've done 8 so far... on this particular unit I also added cab window shades that I made and filler between the top of the truck to the frame.

The 3 to 2 rail MTH wheelsets I purchased were 2 of the 4 complete axle sets, none of these axles were grooved to accept the axle gear that contacts the motor pinion. Looking at the blind 3-rail axles on the center of each truck I may be able to press off the 3-rail wheels and press on the 2-rail wheels if I can come up with the right tools. It would be simpler to just drop in a complete 2-rail assembly.  

you need the six wheel set, save the four wheel set for a future diesel with two axle trucks.

 There's a few of us here that do this. I've been reading and watching what's posted. It is hard to get the fixed pilots from MTH. When you can, I believe they're like $25 each. Then the railings and other parts I've never been able to get.

 So most of us adapt the pilots I believe. It is so much easier to get the two rail version. Sometimes there isn't any ever made. All their dummies are only available in three rail for example.

 I've just made a shim like Jeff describes to fill the gap. Each engine has a different challenge but mainly the same proceedure. Get the six wheel set and make fillers, mount some KD's and fill the gaps if desired. The railings I still haven't fixed myself.