Live Stream Score Overlay

Ok lets assume that everything works perfectly. The camera interfaces with the computer perfectly, OBS works perfectly, everything is perfect. How would I get the field score overlay from the FRC field onto the live stream? I am just talking the hardware side. Ho do I get the overlay onto my computer so I can put it on the live stream?

Here is the info I found. I have been trying to figure this out for some time, but finally found the info I needed.

http://www.andymark.com/product-p/offseasonfield.htm

If I remember correctly the FMS PC outputs the score display in composite or VGA, so look into a capture card. You can crop out where the camera feed would normally be on the score display and overlay just the score info onto a nice HD video feed.

EDIT: not sure if OBS supports cropping. Chroma key might be possible instead? Xsplit supports either method.