I don't know how many stalls are in an old west stock car. I know there was room for 8 in old European wagons "40 or 8"... 40 soldiers or 8 horses.
I think one of eastern roads (B&O) made a roofless stock car pre 1850 for a while, but it didn't last. (Neither did slings and a few other practices)
High sided gondolas got mentioned for moving cattle sometimes in some reading you had inspired. But no mention of corrals on a flatcar anywhere.
Water and feed enroute were the main concerns and the design changes that mattered it seemed.