Stephen Hulsey

My son and I have swapped the original 4.8 Vortec to a used 5.3 GM crate with ~100,000 miles. Do I need to order a brand new PCM/ECM VIN programmed and updated from Flagship One or can I have my old unit tuned? Pardon if I'm using the incorrect terminology but we decided to use this project as father and son. If I purchase a new unit, will I need to have it tuned? Basically what are the next steps I should take from the electrical side as all other mechanical parts have been finished. Thank you all.