Injection wiring.

I have recently bought a Kreg 3.9 RR and want to transplant the engine and box into an Iveco motorhome. I am slightly confused as to exactly how much of the RR loom I will need. I have traced the engine wires from the dizzy back into the car and they end at the dash plug. I am presuming these are senders for the temp etc. The loom from the injectors goes to the computer but there are many other wires here as well. What ones are needed and what can be cut. Any ideas or info would be extremely useful. Thanks Kev