I have a 2003 suburban with a 5.3 and have changed the plugs.
I used AC-Delco 41-962 per bulletin https://images.oreillyauto.com/parts/img/documents/acd/41-110.pdf
gap at .40
A few of my wires broke during replacement so plan on wires as well. I used Delco wires.
The back plug on the passenger side is the toughest. I used a couple wobbles and a couple of extensions.
FYI while you are in there... do u ever feel a slight clunk in the steering? If so remove the bolt in the steering shaft and push and pull the shaft towards the firewall and towards the front a few times. It lubricates the joint with grease that gets dry over time..
I also did both of my front 02 sensors while i was at it.. and kept them as spares in case the back ones act up.