Great progress, two questions.
Did you make your own coupler return springs?
Did you wire the motors in series?
Very interesting project, John. Nice upgrade.
Thanks, it'll be more interesting when I finally get done! 
Here's a few more progress pictures, I think I'm knocking off for the day.
The posts in the rear half of the frame for the old PCB mounting (where the CC-Lite will go) had to be chopped off, there isn't enough clearance if they're there. Turns out it's a pretty tight fit, I had to jockey the position of the board to make it fit without the posts, I have to account for the truck mount screw sticking up.
Since I'm using LED lights, the CC-Lite requires these .01 caps across the light outputs. The easiest place to put them is under the R4LC, they take no extra space and they're totally out of the way.
I couldn't use the existing little light boards, though that was my original plan. I made up these light harnesses with 2mm warm white LED's, a diode, and a 470 ohm resistor. Each one will connect to the appropriate light output on the CC-Lite
Here's one of the lights positioned in the shell, a couple spots of CA adhesive in the corner and they're all set. The other side is identical. I'll eventually add a cab light on the floor of the cab and control it with the smoke output, that will be an incandescent as they make nicer cab lighting.
