Here a few photos of the Bachmann 45xx chassis with the new Ultrascale P4 wheels temporarily in place with the Bachmann coupling rods and motion. I've added plasticard overlays to bring the 'frames' out to something a little closer to prototypical dimensions as I just couldn't live with the scale 18" gap behind the wheels that there would be otherwise!
When I originally mentioned it I thought there was a problem with the crank pins on the front wheels fouling the motion brackets. What I hadn't realised at the time, which is pretty obvious now, is that the protruding ends of the crank pins require trimming once the rods and motion are in place. So there isn't a problem after all!
More photos when I've made a bit more progress.