I am installing a Uniden CB radio in the spot where the ashtray and lighter used to be. THere is power there from the lighter but I don't know which wire is grounded. Is it positive ground or negative ground? 4.9L IL6 EFI motor 4x4 w/manual transmission.

 

It's negative ground. Positive is the wire going to the lighter, center button in the socket, it grounds through the shell.