Thanks for the info arbomambo!
I got the castings today, and will try to post some phone photos of them later. They look like I will need to cut off the Kato pilot entirely and get a set of MT's to replace the Kato coupler parts.
On the proto info side, my understanding is that Amtrak added the plows, and maybe the icicle breakers. I'm not planning to fiddle with the breakers because it seems once the units got reassigned to Cleburne for a while a while, they were removed. They used units in pairs both because of engine reliability and steam generator reliability issues. The Inter American ran over the MoPac, which slapped a 40 to 60 mph speed restriction on the train from when it started in 1973 until 1978 or so. The MP also supposedly hated SDP40F's, and I have only seen one or two photos of them on the Inter American. But they only needed one when they were assigned!
I'll eventually be back looking for the best way to replace the side panels where the portholes were blanked and where on earth to find the UP snowshields on N scale (I already called Broadway Limited's parts department and came up empty).