Roger those are great pics thanks! That funnel looks just like the one that was OEM in my LM Challenger. So it's just possible that the same 3D printed funnel will work in both engines.
If you have the time, can you confirm a couple of dimensions for me? 1. Outside funnel bowl dimension, front to back (Eg. 31mm) 2. Center of bowl smoke opening to outside front of smoke unit body casting (Eg. 17mm) That would help to confirm things.
Can you also provide the product number for your Bigboy please. Then I can maybe check out the part number on Lionels parts site and see if the OEM funnels are indeed the same part.
Many thanks!
Rod