Where to tie in on a good electrical point (underdash) for newer Chevy P/U?

[77 ChevySport]

Try to make a long story short. Will be adding a GPS system that needs 12 Volts to
go on when engine runs;off when engine shuts off. GPS system will augment my OnStar.
My application is a 2014 Silverado. Where is a good/simple point to tie in and get this voltage? We all know with the older vehicles it was as simple as running a wire to the open fuse box. How about these new vehicles? Thanks in advance-Larry

P.S. Wonder is GM give some extra electrical points for this. (GPS's-CB's and etc)