I'd like to swap my 4.8 to a 5.3 in my 2001 silverado. From what I understand the two engines are (from a mounting point of view) identical - however I was recently told by a representative from powerpro 2000 that the wiring harnesses are different. My shop told me that it is doable - even driving there to have my computer re-programmed. Legally I believe I am ok as long as the truck came with this engine as an option and the engine is newer than the original one. Does anybody have any experience in this? What are your thoughts?? Jake Happy owner of a 2001 Silverado Z71 with approximately 137000 miles on it.