assuming you are talking about the trip computer

you will only be able to fit them to the dohc engine or the 2.9 engines as they are specific to those cars

they use an injector opening (4 for the dohc 6 for the V6 which is why you can't swap them around) timing system to figure out how much fuel you have used and the speed sensor to work out how far you have travelled

you can't fit one to the 1.6 as it's got no injectors