66 Mustang blows accessory fuse when ignition is turned on

I just bought a 66 Mustang project car. It has a fuse blowing problem. The 14 amp accessory fuses blows as soon as you turn on the ignition.
I found a lot of wiring diagrams that say the fuse (number 1) controls back up lights, radio, PRNDL light and turn signals. My turn signals work fine.
I don't have a radio, nor does the car have backup lights. I found the connector for the PRNDL light but it is unplugged and I can't see where it would go.
I want to isolate the circuits so I can find the short but haven't found a good starting point yet. The radio appears to be on circuit 140, black with red going to a yellow 3 way plug. I unplugged what was in the yellow connector but still have a short. There appears to be another wire hooked to the fuse but I can't find it on the wiring diagram.
Can you guys help me understand this? What else is hooked to the number 1 fuse?
Thanks
Dan

Thanks for moving my thread.
OK, I have more info. Here is a picture of my fuse box turned on its side and the wires spread out. It clearly shows a second wire going to the accessory fuse. The Black-red wire is in all the diagrams. The White wire isn't in any diagram I found.
Where does this white wire go? I found wiring info on the internet showing all wire colors for 66 Mustang. There are only 4 white wires (35,58,95,806). I can find 35 white wire in the alternator to regulator circuit. 58 wire is in the wiper circuit from switch to wiper motor. I cannot find 95 or 806 wire on any diagram I found. Yet my fuse box clearly has a white wire going to it. I believe my white wire is shorted to ground somewhere but I need to know where it goes to unhook it and check for a short.