Did the manual at Sears not have a parts breakdown in the back? The belts are 579932MA and 581264MA. That was looked up at the sister site searpartsdirect.com
and had not no picture.
To tell you what you have; it is a Noma(Dynamark) snowthrower made for Sears. The company was bought by Murray which was was taken over by Briggs & Stratton because of outstanding debt. All factories were closed and the manufacturing responsiblities were transferred to AYP(who has made most Craftsman equipment for a long time.)
There is another site that has a similar model number manual on it. LawnandGarden.ManualsOnline.com - We found it so you don't have to!
where I found a picture. I will try to attach. Understand that most mechanics have little more to go on than this. Where the belts curve inward means that a pulley is touching the backside(outside) of the belt to engage.