1981 chev pickup - no electrical power

Driving down the road, my '81 chev truck lost all electrical power. No radio, dash lights ... nothing. The battery is recent and has been tested with a voltage meter and is good. We also tested at the starter, and the
power is getting to the starter. After the starter the wires seem to go to a rather useless(to me anyway) device that has two connections, on the firewall beside the brake booster. It looks like a ground. No power registers on the volt meter( I don't know if it's supposed to, but it seemed logical to trace the power from the baterry and on from there.)
I don't understand why ALL electrical power throughout the vehicle would fail. At first thought, it must be a ground, but all other grounds seem fine. Could it be something as simple as a fuse, or since the age of the truck, the whole fuse box itself.
If anyone knows of a diagram somewhere on the internet of the '81 engine bay, I could start with that.
Any advice is appreciated.
TIA.
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Down by the starter on one of those wires has a fuseable link in it, my guess is it went bad, this is a little block within the wire, when you find the block take each end in your hands and try to pull it apart, if it pulls apart than it is bad, I usually just by pass these but you should really goto the parts store and pick another one or two of them up.

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I had a similar problem with my '89 Van. It turned out the connectors (spade) that attach to the fusible links in the firewall "block" corroded away!. I went to a junk yard and got one from another van, removed the spade connectors (and wires) and replaced there fusible links and coated the terminals with grease put it together, and sprayed the whole mess with undercoating. Frank
Monte-Carlo wrote:

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