The 460 and 480 threshing systems are the same. So, whatever you consider changing on the 480's threshing system might have to be considered on a 460 too. I know that spike tooth systems are frequently used in the Northwest on machines whose use is strictly grass seed. No matter the type of combine (460 or 480),if you are not using small grains pre-concave grates (6.5mm x 40mm) for grass seed you won't be threshing at top performance with either machine (dis-awning plates open or closed, you need the texture of the small grain grate). Ensuring proper pre-concave grates needs to be your starting point. As far as using a spike tooth system, if your machine is going to be used in other crops (i.e., corn, beans, small grains) consider only changing the twin rotary separation system to spike teeth and not the threshing system. I would still try running a rod (3_4" dia.) parallel to the rotors and fastened to the bottom side of the cage before changing rotors. If you do choose to go with a 460 make sure you invest in a full set of fishback risers and the Intensive Separation System (ISS) to make separation more agressive.