Before I quit buying things, I got, from eBay, an MTH former PS-2 ESE J3a Hudson. Cheap. A "kit". It had no motor, boards, driveline and so forth. Don't know why I bought it, as I already had an ESE (Lionel) or two.
Anyway, now, some years later, I figured if I was going to sell it, it needed to run in order to get any sort of price at all. So I ordered all the needed parts from MTH (love the new MTH Parts on their website; gee, it's almost like somebody formerly with Lionel designed it....) and installed them.
Then I scrounged through my e-unit stash (from upgrading locos to TMCC) and found one from a Williams 4-6-0, with bell and whistle.
Afterwards below. Totally conventional with track power headlight (14V incandescent bulb). No sound, smoke or (functioning) P'coupler. It's a modern interpretation of a PW loco. It just runs. And well. FNR. I had no idea that the gear ratio was that good. Smooth. Quiet. The Wms bell/whistle are fine.
Of course, now I don't want to sell it.....trapped again.