what all will we need to be changed? can we use the wiring harness out of the 03 and the ecm or do we have to use the wiring and ecm that is on the 05 engine both are manual trucks.

 

What are you swapping into what???

If your putting the 05 engine into the 03, use the 03 harness and ECU. Swapping in the 05 electronics is not going to work without a lot of hassle.

 

not to be smart but I would say I needing to remove a cummins from an 03 and I have a cummins engine out of an 05 truck. what all should I use since I have all of it 05 wiring and ecm or retain the 03 wiring and ecm and what about all the other electrical hook ups are they the same and can I use the 05 injectors with an 03 ecm if i have to use that ecm?

 

Just checking to make sure we are talking about the same thing.

IIRC, use all the 03 electronics and harness while replacing just the motor with the 05 injectors and all.