The correct way to do it is to replace all the rollers ,the front idler(they have a different shape)and the tennsion spring assembly or add a spacer. There is also guide plates that bolt on near the front idler. The wrong way to do it is to simply put the guide plates on and fit the steel track I have seen this done without any problems.
Check the Hybrid steel tracks with rubber pads that McLaren offers (www.mclarenusa.com). They say you don't need to change anything when converting from rubber tracks to their Hybrid tracks, but I'm not sure if they have Hybrid tracks for your Bobcat 331. From all I know, if you want to switch to a regular steel track, you'll need to change rollers, idlers, etc.
Generally your dealer will have a good idea if you need to change the undercarriage or not if you decide to change over from rubber to steel. Some equipments don't and some do. The great thing about our Hybrid track is that they are designed to fit onto your rubber track undercarriage. You do not need to change out any undercarriage parts. And with our Hybrid tracks you can choose to use them with or without the pads. They are connected together by a master section which is held together by a master pin and a retaining pin so the installation is much easier than getting on a rubber track!
Hope this helps! www.mclarenusa.com