I have a 99 silverado, newer bodystyle.4300 V6, 4l60E. Any issues that come to mind with installing a LS1. Can i reuse most of the engine harness? can the PCM be reflashed for the LS1 or do i need to swap it and the harness. I have not bought an engine yet. I figured a LS1 should pull a camper and get decent fuel mileage. Some say to just install a 5300. Any help would be great

Joe