I just purchased a 2020 2500HD and had the gooseneck hitch installed. But it didn't come with the wiring harness (standard on the 3500) or the 7 pin/4 Pin plug in. Chevy kindly predrilled the hole though, so I am limited to getting the exact size to ensure it covers the entire hole. Problem is, the parts department cant figure out which part to order. They keep wanting to give me the one listed online which is too small to cover the entire hole. Anyone find an aftermarket one that works?