Harleyizy,
Didn't realize your post was from 11/2011 but anyway I figured out how to level out the snowblower attachment. I took the side that was the lowest (drooping) and did the following:
1. Lower the snowblower to the ground so all the weight is off the snowblower and undercarriage.
2. Find the lift link on the side that droops. Part #22 (three holes at the bottom and slotted top)from:
Parts and Diagrams for Cub Cadet 451 45" Snowthrower
3. Detach it fron the undercarriage at both the top and bottom pins.
4. Install a rounded spacer on top of the top pin the slotted end the lift link fits over (a 1/8" thick spacer raised this side of my blower approx. 1/2")
5. Reinstall the lift link and check the level. Repeat with a thicker/thinner spacer if needed.
I just thought that you could also, in theory, take the side of the blower that's higher, file the opening in the lift link slot at the top and make it have a longer slotted opening, and thus let the higher side drop. This could be the better way to go since it would be permanent, and you wouldn't have any shins to worry about. You could also keep taking it off, filing some, and putting it back on until you got it perfectly level. If my spacer doesn't hold up i'll probably try that next. Wish i'd thought of that first, but it was getting late and I was happy just to get it leveled! Hope this helps somebody.