I'm not sure of the class; for one thing RC didn't have pictures of the underframe on the web site. But the ends are closed so that rules out the S-40-8 and S-40-10 judging by pics in Tony's book. I'm guessing it's S-40-4, 5 or 6 and those would be in common with the UP. I don't know about IC.
It's very cool that Sunshine has announced the SP S-40-12 & 13 too. These cars fill a huge void for the average SP modeler of the 40's or 50's. (Westerfield has long offered SP stock cars but they are not kits for the 'average' model train enthusiast.)
