03/04 LB7 to LLY no re pinning needed, just install the LLY body side harness with ECM where you remove the LB7 harness. Since you’re most likely keeping the LB7 trans, keep the LB7 TCM. If you install an LLY trans, use the LLY TCM. If you get a complete motor and harness, ECM, intake, LLY NSBU...