Next to a front-end loader, a chipper-shredder may be the most sought after attachment for these old tractors. Check out this one that Terry Benander has -- it looks like it's in great, unrestored shape...
Click each picture for a closer view
Herb suggested that I send you these MacKISSIC chipper pics, as some people may like to see how it attaches, etc. Although you can't see it, you have to remove the rear lift bracket, and put straight bar stock in it's place. The top mount of the chipper just hooks on to that rod. I also would think that if you had a remote PTO control (like on a 3415S that I have), you would not need the actuator/tensioner setup -- just an idler to tension the belt.
If you need more pics from a different angle, etc.... let me know!
Since this desirable attachment fits both Simplicity and Allis-Chalmers and was marketed by both dealer networks, I thought I'd add it to "Mix and Match" section. Kent