Wait a second. It shows the 4120 and the 4720 in one area (pages 3 & 4), and then the 4320 and 4520 in another area (page 8) with a "cut" added to differentiate.
Also interesting to see the 4720 listed at it's original PTO HP of 50, and the 4520 at it's original HP of 45. Guess the tweaks and changes would be too much to keep up with or would clutter the list.
Odd breakout....
Pete