What is the difference between the John Deere 8R 490 and 8R 540?

Here is how the John Deere 8R 490 and John Deere 8R 540 compare on John Deere's published specifications:

• Weight: John Deere 8R 490 37377 lb. vs John Deere 8R 540 37377 lb.
• Wheelbase: John Deere 8R 490 131.9 in. vs John Deere 8R 540 131.9 in.