The main hot wire to the ignition burns up fusible links and now fuses when the motor quits or is shut off. The truck is a 1980 Scottsdale 20 with a 400 ci engine.

The power goes from the battery to the fuse box and then to the fuel pump relay, so just concentrate on the fuse box. Depends on vehicle and model whether fuse gets power anytime the battery is connected (hot at all times) or only when the key switch is in "on" (hot in run or start). You have a test light to check for power at the fuse terminals? That is how to start.
Some older models used "fusible links" in major circuits to distribute power, like to the fuse box, or to the ignition switch. The links act like fuses to protect wiring, they will "blow" or burn out if a big short or surge tries to damage wiring. Then you can just cut out and replace the fusible link. Nowadays, they mostly use maxi-fuses instead of fusible links, but you would need to consult a wiring diagram for your vehicle to really know the set up.

Make sure battery has a full charge and battery connections all good. Follow one of the + battery connections, may go to a bunch of fusible links, there should be voltage on both sides of fusible link or it is faulty.
Or, pick one component that is fuse protected and doesn't work, check that fuse circuit for voltage, use a test lite. Some fuses are hot all the time, some go hot with the key on. What is litre size of engine? Is it 4wd or 2?
One wiring diagram I looked at, had two red wires carrying voltage to ignition switch, hot all the time, if you think problem is ignition feed?

Check the main fuses. Should be high amperage, large fuses.

You burned out a fusible link at the starter motor. The wiring is shorted to ground down there somewhere. Raise the car up and inspect for the damaged wiring and then replace the fusible link. The links are color codes for amperage, most are 30 amperes.

Look for a "fusible link" in the red wire going from the battery to the firewall or engine compartment fuse box. This is generally a smaller size wire inserted in the bigger wire, and it has molded-over connections to the larger wire. If you see a burned spot on the insulation, it's a good bet you had a major overload that fried the link. If you don't, flex the wire to be sure it bends uniformly - if it is broken, there will be a spot that bends too easily. In most vehicles the fusible link is in one of the cables running across the top of the firewall just below the windshield wipers.

If the fusible link is burned out, remove all fuses except for ECM, IGN and FUEL (i. e., strip out everything except what you need to make the engine run. Replace the fusible link with the same size and length of wire as the original. Start the engine and feel the new link to see if it is getting hot. If not, install the other fuses one at a time with all accessories turned off, and check the link each time. Make sure you are installing the correct fuse size in each location. If at some point the link starts to get hot, you have a clue as to which circuit is overloaded. Inspect the wiring on that circuit, and if any devices on that circuit are not working normally, repair them.

The fusible link may also burn out if you have an over-sized after-market audio system powered through it, crank it up while the headlights and wipers are on, then hit the brakes or honk the horn (i. e., excess total load).

The wires and the fusible links at the starter should be checked, and you will know a bad fusible link wire when you find one, because they will stretch like a rubber-band, and repair any fusible link wire that you find that are burned out.

If you can not find any problem with the wiring or fusible links at the starter, then check the "start" fuse for the starter field wire, (if it has one it will usually be located out in the fuse/relay junction box) also the starter field wire should be connected to the "S" terminal on the starter solenoid and it will be "hot" or have power to it only when the key is in the "start" position, and if the field wire to the starter is the wire that burned up then the ignition switch itself might have been damaged.

Most starter circuits will have a fusible link in them. That is basically a wire that goes from a heavy guage, to a smaller guage in the middle, back to the heavier guage wire. The point of it is that if the circuit gets too hot, the smaller guage wire will burn, acting like a fuse. Check the wiring. A burnt fusible link will be visible by bubbled/melted insulation on wiring.

Ensure that the starter bolts are also tight, as that is how they ground out.

If the wiring is all OK, then i suppose you could suspect a faulty ignition switch.

If, when the switch is turned, the starter motor does not operate at all but the solenoid clicks, the problem lies with either the battery, the main solenoid contacts, or the starter motor. If, as you say, the battery is good, and fully charged, that would mean that is was either the solenoid contacts or the starter motor.
If the solenoid plunger cannot be heard (no click), the battery is bad, the fusible link is burned, or the solenoid itself is defective. Once again, if the battery is good, it would be the fusible link, or the solenoid. The fusible link (battery fuse) is in the engine compartment fuse block, fuse number 1, 80A.
If you want to test the circuit, you can run a fairly heavy INSULATED wire between your pos. battery post and the SMALL terminal on the solenoid (just touch the end to the solenoid). If the starter turns, you may have a ignition switch, neutral start switch, or some other wiring problem.
Double check the battery terminals to make sure that you are getting good contact.
Hope this is helpful.

use a 14 gauge link for a 30 amp requirement.

Check the fusible links at the starter. One of them may be burned. You mentioned that it shuts down when you turn a corner. Check the wiring going to the ignition switch under the steering column, you may have a loose wire there as well.