Shamus,
I'm guessing, but that 50 ton class B sidewinder #3 looks like a Model Die Casting engine. I have one of those kits, and haven't completed it because I can't get it to run as smooth, and as quiet as I want it to.
I am working on an idea to use "V" belt drive to the engine crankshaft to provide drive through the side gears, and have removed the original worm drive. All that remains of the truck gearboxes is the bolster area. The drivers have been re-installed on pointed axels, and the sideframes modified to accept those axels. The engine coasts very smoothly, and if I can't get a drive mechanism that works, I can still "dummy" the engine with a Bachmann spectrum.
If you think I'm completely mad, patronize me, I'm also reworking an Arbour Models Allegheny kit with new drivers, and full working equalization, and I still have more trees to grow.
Great photos !
Pete