The T18 swaybar mounts are slightly different to Sprinter ones. The metal clamp for the bushing is bigger on the T18 and mounts slightly differently. So to make it work you need to either use your T18 swaybar bushes and T18 metal clamps or cut a slot in the mount to use your sprinter bush and sprinter metal clamp (for example if you have an aftermarket, bigger swaybar).
Don't worry, once you look at it it's really obvious, it just takes a bit of time with a drill and file to make the slots.