Although mentioning he’s aiming for the transition era doesn’t completely disavow all modern brands… Athearn and Intermountain have a few GP and F units that would fit that era nicely, and Rapido has their own fair share of transition stuff to.
But I can understand the frustration of grab irons breaking off… I had that happen to me trying to use a 0-5-0 to rerail a derailed tank car at an operation session I was at, and then having to go through ‘reporting the car damage’ to the railroads owner. Or that time my cousin’s sent my Athearn SW1500 on a trip from table top to the floor and I had to re-glue a piece that fell of it due to that encounter with gravity. If durabiltiy is the primary goal then those simpler older locomotives probably have a lot of points ahead of the finer detailed units of now.
People get pretty ham-fisted at our club layout, and the newer, more detailed locomotives get broken easily. I’m afraid to leave my Bowsers and my (one) Athearn Genesis on the layout. Older locomotives like Athearn BB, Proto 1k and Walthers Mainline are perfect for our club – they are durable, the mechanisms are strong and bulletproof, and there’s little to get broken if someone lifts a unit off the rails a little too quickly.
I think the OP’s time frame and need for metal 'rails narrows his choices, but the old stuff still has a place.
Diesels made by ATLAS TRAINMAN and WALTHERS TRAINLINE have simple details, few pilot details, and robust handrails. They typically run better than most Bachmann diesels.
I know Atlas makes an RS36 that’s a nice loco. Their Trainman series requires the owner to buy the proper grab irons and install them on their own, but the model has drilling dimples as guides.
Also ATLAS CLASSIC SILVER makes a nice ALCO RS-11 that has separately applied metal grabirons but handrails that are on the thick side, as well as few pilot details. Same goes for the ALCO RS-1 and RS-3
If it was me, I’d buy one from the 2001 to 2012 vintages when they still had the Kato cloned motors. They pop up on ebay frequently.
All come with coupler boxes that can accomodate Kadees or NMRA Horn Hooks easily.
I’d second the suggestion of Athearn Blue Box. They’re easy to find, easy to service, sturdy, etc. I like that I can hand them to my kids and not worry that something is going to be broken off.
I’ve got quite a few that meet your criteria and I’m quite happy with them. Finding ones that have been assembled (often with added grabs and such) is easy and it’s not too hard to find like-new unassembled versions. My local trainshop “Zientek” has quite a few NOS unbuilt BB locos.
OK, well, some people have figured out ways to mount the box to the shell, and they cut off the little casting that the plastic box snaps onto.
The problem with using the little casting, which is part of the frame, Athearn’s electrical path goes through the frame, and with metal couplers, say like Kadee’s, that could cause a potential shorting problem, especially if you couple 2 Athearns together, back to back, unless you insulate the couple from making contact with the frame.
I don’t know much about Sargent couplers, if they are metal or not, but just passing this on FYI.