'87 Silverado TBI swapping to 5.3L here...

Everything is straightforward to me except the wiring situation. If I was to get a new harness, or have the 5.3L harness modded do I need to keep my stock TBI harness?

I ask because a guy wants to buy my complete engine/trans/harness and I don't want to make a mistake getting rid of the TBI harness.