I'm into the really meaty part if this job now, the MARS light on the Berk.
Ok, it's a pretty lousy picture, but I'm still taking all these pictures with a cellphone. (still haven't replaced my camera since the Nashville Flood in 2010.)
So in the foreground on the right you can see the Lionel MARS light. It's cast in one piece with the bracket. On the left is the brass replacement, which is scale sized. As you can see, the Lionel piece is oversized. Once I starting working on this, it was easy to see why: it's hard to fit everything into the scale-sized housing. Also, the Lionel light runs the wires out the back of the housing and straight through a hole in the smoke box door. That's not the way the NKP did it.
So I'd love to hide two wires into a scale conduit, but I'm not THAT good. So one lead from the LED will exit the back of the housing and down to the bracket, while the other lead will exit the bottom of the housing and through the bracket.
That's not the only fun part. To make everything fit, I filed the tip off of the LED to shorten it. Also, the brass piece didn't come with a lense, but it was not big deal to mount the Lionel lense on a rod and chock it on my drill to turn it down slightly to fit in the new part.
So that's where that is.