Jeff,
to further compound the issue, i believe the under-frame and trucks you mention, supposedly from C&S 8308/RGS 8714, are actually from RGS 8716, which I believe was renumbered to 8714 at the time the remainder of the cars went away C&S 8208/ RGS 8716 was also an outfit car. there has been speculation over the years that at some point the RGS removed the roof hatches. what i do know is the end buffers on the car miraculously changed at some point in its life, and given that they are riveted to the under-frame not something easily changed. if you will note in the attached picture that 8714 with roof hatches has the buffer typical of the second group of boxcars, and the stock cars.
where as the under-frame in question has this style of buffer from the first group of C&S cars
it is also quit possible that the roof leaked around the roof hatches, making a little # swap for the crews using these cars worth while. also note that the car numbers are exactly 100 # apart.
Al P.