What are the differnces between the 3.9L and 5.9L Wiring Harness and ECUs? If I put a 5.9L in my stock V6 Dakotat will I have to replace the ECU, Wiring Harness, or Both or Neither? If neither do I just get a tune? Sorry I am very new to the dodge truck world, not to mention the computer controlled era. I own a 75 vette with out a computer where engine swaps are pretty simple tasks in comparison.

Thanks for any help.

Josh