I know this is a commonly brought up topic, but the N scale 4-4-0s can be remade with a motor in the boiler/cab, I am currently reconstructing my first 4-4-0 to have a coreless motor in it's boiler. The biggest problem I'm facing is the wheel alignment, they keep jamming & I think they aren't quartered correctly. I'll try to fix the quartering issue, but if it doesn't work I'll update this post & ask for suggestions. On the other hand I have to rebuild the tender from the ground up because the old one is broken.