I have a Stevenson 0-6-0 kit I plan to do the same thing with. My plan is to get driver centers and machine three rail big flange tires for the centers. The only question mark at this point is if the frame ia narrow enough to accomodate the wider wheels?? Winter project.
If you don't have a lathe maybe you can get a set of wheels from an existing three rail egine and try and fit them to your engine.
Edit, you may find a three rail Mikdao that the Stevenson body will fit on. My Sunset NYC K5 Pacific would not fit on an MTH Pacific Frame but that doesn't mean yours won't fit on another Mikado frame.
Pete