This post would not be possible without the help of Rod Stewart and Gunrunner John. I decided to build the PCBs that connect to the LED strips and convert these cars to all LEDs. There are 5 of them and I have only converted one of the coaches so far.
First, figuring out how to take the car apart was my first challenge and of course I made it more difficult than it is. All you need to do is remove 2 screws that hold the undercarriage plastic box on and then the 4 screws, 2 at each end, that hold the plastic end caps on the aluminum extrusion. Then you just slide out the entire floor with the trucks staying attached after sliding off the end caps.
I built 12 of the PCB kits and put two strips of Led lighting on the roof underside, about 15" long each with 7 segments of 3 lights on each side of the inside rib that held the stream lighting board in. See picture. I used 3M sticky tape on both sides to hold the Led strips in place.
Finished product. One on the right has the LEDs and I also added passengers.
Looking down inside the roof to see the LED rows. It ended up being 42 lights! Gunrunner John recommended the two strips on either side of the rood ridge. 
I mounted the board on the plastic surface of the end piece with two sided sticky tape. While it can be seen through the window it is not obtrusive. Also it easy to make a light adjustment because all you have to do is undo two screws and slide the end off! The other end has the doors and a vestibule but you would have to redo the truck wiring to make a simple hook up at that end. The PCB will fit inside the vestibule if you wish. Soldering is a bit tedious if you aren't used to it, but I did ok. By the way the strips will need jumper connections on the other end(not shown). You only need to feed one end with DC current, it will light both strips on problem. 
This shot is with the LEDs full bright on the right car. I turned them down quite a bit.
This is the final setting. 
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You also have to unhook the plastic end of the wiring to the lights. Sliding out the entire floor is difficult due to the tight fit. I recommend you use a wooden stick to help push on the metal floor and use your other hand to hold the aluminum sides apart just a bit. It will come out. You can also tap it with a hammer.
I hope this is somewhat informative. Unfortunately I am not good at photo shooting while I build something the first time. If you have any questions just ask. I will be happy to answer. I basically used the ideas in Rod Stewarts topic about LED conversion and bought his kits. They were well thought out and they worked and I am not an expert with the solder gun! I used the .080 solder and a fine point as recommended.
Rod also recommended to paint the LEDs if you want to tone down the light or slightly change the color.
I did this mainly to prevent bulb burnout on the stream lighting, less power required and a warmer 'look' to the interior. Only four more cars to go!
