The Radio and a rev-cam if you want one.
You’ll need pull-outs if you want to add speakers to the hab area.
While the radio is out, you can fit a reversing camera.
Switch ignition off. Disconnect batteries to be on the safe side. Remove the radio. Use the wiring diagram which comes with the radio to see which connection is which.
About the only things omitted when we collected our van from the dealer were the pullouts. However , we were assured they were on their way. However , they have not arrived and it's now June 09.