[ChevLoRay]

You said that the radio was hooked to the junction block. It has a memory circuit, and that circuit consumes power all the time. Did you guys sit in your truck and listen to the radio, while waiting for the tow truck?

If you want to find the source of the "short", be sure you have a hot battery before starting the following procedure. With the battery disconnected (one terminal only), pull one fuse to eliminate, let's say....the tail lights. When you reconnect the terminal, look for an arc, or listen for the sound that the arc makes when you touch the terminal to the post. If so, then the bad circuit is somewhere else. Keep pulling fuses until you find the circuit that doesn't make the arcing (flash/sound) when you reconnect the terminal to the post.

You might be amazed at what you find.