That "Junction block" connection seems to be a recurring problem with these trucks, double check the red fusible link (wire) coming from the battery positive cable to the junction block (small black triangle/insulated block on the fender, next to the battery tray) and make sure the terminal isn't corroded, and/or broken inside the insulator.
take a test light and probe the insulation to see if there is battery voltage available. You said something about a new key, did you replace the whole switch or just the key? The connector on the back of the switch can be hard to connect, look at that too....
Hth,
Ben Smith
