Don't know what yr model mine is. I just bought it last weekend and it had a belt that was waaay too narrow. Tried a B-27 power transmission belt from my local brg and v belt store. It worked OK for a little while and shredded. I think it was a little too long and overheated due to the backwards wrap around the clutch idler pulley. I got a B-26 this time and it seems to be holding up well.
HTH,
Mike

You can match up the belt at an auto parts store if ypou happen to have have the correct old one.

What I did was to go on ebay and look up chipper /shredder / mulchers and found a couple venders who sell the belt we need. It cost me about 15.00 for the belt and I bought new flails and chipping blade while I was at it. I love these old machines (I use mine several times a week) and I'm glad that the parts we need are still available.