One of the more perplexing questions was what to do for the smokestack. First, the MTH stack had a cast-in nipple that extended into the smokebox and mated with a cup on the smoke unit. I cut that off so I could re-use it. Second, as you can see at the top, they Southern used a very specific design with a collar on top that is not available in O scale (not even PSC). Luckily, I had a length of copper tube that was the correct diameter. I glued in the bottom part from the original stack, and built up the collar with JB Weld. After much sanding and filing:
Here you can see the front running boards I just put back on, built up to be wider with, you guessed it, JB Weld. It's starting to look like a locomotive again!
