If it's the same build generation, then yes you can swap the internal components. If your 1 GHz Ti has FW800 then it's a newer gen and the casing won't be tooled correctly to fit. If it doesn't have FW800, it'll be the same generation. In that case, yes, you can swap your 1GHz logic board and all components into the other case. (You'll want to swap the entire logic board, not just CPU, so you keep your 64 MB VRAM rather than the 867's 32 MB VRAM -- makes a big difference.)