Is it possible to put a LLY engine in a 04 3500 duramax that has an LB7 or is there to many electical difference or any other problems. Thanks for the information in advance.

 

You can do it, either go donor truck route for harnesses and ecm or I have read where a guy used all lb7 electronics on the lly and changed the injectors harnesses over at the ficm connector. It would be easier with the 04 truck than 02 and down since you have the same cluster as lly up trucks if you can source harnesses and modules.