That is for the old Toro Suburban tractors the ones that look like the pics rydogg posted.
I have and still use that exact same blower on my 1967 10HP Suburban model 55300. I am in process of rebuilding and some modifying on my blower right now hope to finish sometime this next week, before my luck runs out and we get snow.
My tag is gone also so can't help on the model number. I have searched and searched the Toro site, google, etc and can't find a blower that looks like that listed for any 60's or early 70's model years so not sure what is going on. I doubt they still make any parts anyway but would be nice to know the model number so if you ever find out let me know also.