I recently got one of the original 1994 MTH Premier Union Pacific 3985 Challenger PS1 engines off of eBay about 3 months ago.
Item# is 20-3002-1 and it came in better condition that I'd expect, which is awesome because the engine was one of the last listings for that specific model in a long while (I still haven't seen any listings like it).
I would love to post pics but right now my schedule is catching up. As soon as I have time I can get some to put up here.