You don't need another ecm/pcm. All you have to do is get yours flashed for the 6.0 tune, and for any mods you're going to do. It should be a straight forward swap. All the ls serious motors are externally the same. Meaning you can take any external part, oil pan, timing chain cover, intake, throttle body etc and swap the parts from motor to motor with no issues. Only thing you need to watch is, if there's anything specific to your 02, like if your fuel rail is different then an 03--if the donor motor is an 03, which isn't a biggie, just swap with your old parts. I hope I wasn't confusing on my explanation.