I have a 2020 express 3500 ext. I want to put an aftermarket upgrade double din radio in and I don’t know where to find the correct adapters and what all I need, I want to keep the onstar options I just have no idea where to start.

 

Give the folks at Crutchfield a call. If you go through their webpage, they have the appropriate kits that will work. They have pretty good customer service and are good at answering technical questions via email or chat, or just a call. Probably running some deals this weekend too.