Can a newer run ES44 shell (Conrail) fit on the older chassis (NKP) sans working ditch lights? I would like to be able to swap them out depending on which train I want to run it with.
You should be able to swap them out. My only concern would be if the chassis design changed at all if not you should be able to make the changes.
My guess is that the only design change is wiring for the ditch lights. Seeing as the headlight is attached to the inside of the cab and not the shell itself makes me think that will be the same for the ditch lights.