Seeing as how your question has not been answered.
I've used Unimates on anything that is a unit train, which for me are passenger cars and A/B or A/A engine sets, and as front couplers on A units. There are 3 shank lengths; short, medium, long. I have all 3 lengths (its pretty inexpensive), I select the shank length based on how close I want the coupling to be be and how it functions. I normally put the short ones in, however you need to test which one works best for you. The problem with passenger cars is the couplers are on the truck and a long way from the pivot pin. If you go thru an S curve you may need the medium or long shanks to simply be able to pivot the coupler so you don't derail, the short shank does not pivot much.
On some lightweight cars, I put a short shank on one side and a medium shank on the other. Short are too close and the cars hit on tight curves, and medium are too far apart, the combo give me the spacing I need to run on my layout.
They also come in brown/rust and black.
gud luk
Gary