TC 1 is quite different in impementation to 2 and 3. It would need its own harness, CPU and IO boards. I think 2 and 3 may be rom board differences only, but not sure.
4 is also COMPLETELY different. It doesn't use traditional lightguns; the guns pick up infrared beacons positioned around the screen. I haven't seen a 2 or 3, but I would guess the I/O boards are different too.