My books don't mention a 207cui engine for the 580B's. They might have had a later revision in the 580B' line up. But I doubt it, because the last manual I have for the B's was from the final year of production, before the new 580C's. However the 580C was a 207cui. It was a 55hp, unitized main frame. Loader was built onto the main frame, unlike the B's, two part frame. Also the driveline was componetized, for easy removal and repair of driveline parts. The other big improvement on the 580C's over the B's was bigger pins and bushings. The B's got sloppy too fast from wear at the pin joints. The C's corrected this problem quite a bit.
The first run of the 580D also had the same engine as the 580C. Same HP and everything. One big difference between these two machines was the revamped hydraulics on the D series. Also of course was the style of the cab and a few other features, like the clutch cut out button on the loader lever etc. Until the Super D came out about a year and a half after production of the D Lineup. The Super D's came out with Cummin's engines w/Turbo, and was the first Case backhoe to offer 4WD.