engine swap

[bigskydave]

Hi all, I have a 2001 silverado 4x4 1500 with the 4.8 auto. Does anyone know if the wiring harness would work with the 5.3 or 6 litre engine? Also, if it does, can I just get my ecm reflashed or would I have to get a motor specific. I would like to swap out the 4.8 for one of the bigger engines.
Is this doable or would it be a major expense and headache. Thanks for any help on this. By the way, I just joined and this is my first post. Hope someone out there can help me out with this. Thanks again and keep on playin! Bigskydave.