I'm not any kind of expert on UP equipment, being a Burlington Route enthusiast and modeller (1940's-1960's, before BN), but as to the model manufacturer, I would hazard a guess that, from the very oversized flanges on the wheels, I would think maybe AHM/Rivarossi. I agree that Kaydee wheelsets would be a good replacement, along with some Kaydee couplers (unless, of course, you need a transition car for cars using hook-horn (X2f) couplers). BTW, the "Q" and other roads called cabooses "waycars".