If you look at the parts list the special bushing is listed but have never seen one. Always wonder how the 3/4" bushing would fit the 5/8" x 3/4" double-D hole but now we know. The double-D is bigger.
https://www.partstree.com/parts/toro-109916/
Blade shows up here
https://www.wheelhorseforum.com/search/?q=108846&quick=1&type=downloads_file