@Ovie832 The hood is different, the wiring harness for the headlights are different, and there is a plastic sub-frame that is different that you attach the grill too. You will need part number 2 and number 5 from a 2015: If you get it from a salvage yard, they're usually connected together. Oh, you'll also need the fog light connectors. Here's the link to the original post that will give you great details, only you'll follow them in reverse.
https://www.gm-trucks.com/forums/topic/189473-2015-silverado-to-2016-conversion/