Magicland posted:Glad to hear an MTH fan-driven smoke unit will fit, now I'll just have to see if I can track one down.
Here's the MTH smoke unit in the Williams K4. I JB-Weld a spring on the bottom to keep it pressed against the top, and I solder a brass extension tube on the nipple of the smoke unit to direct the smoke out. This one is actually for a different locomotive, I'd probably cut it down a bit for the K4.
The spring and the screw-out extension allows me to remove the smoke unit for service.