I don't believe the lengthy cranking would heat up that wire. The cranking current would come from the battery and most of the high resistance spots in that circuit would be old terminals. If the bulk of the continuous cranking reports come from the 81-87 era harnessitis the remainder might be welded contacts in the ign. switch?

The alternator wouldn't generate the kind of current needed to melt insulation on that 8+ gauge wire at cruising speeds much less cranking speeds, but oil and vibration work over years to create a short circuit where the wire is clamped.

This is also why I have often suggested carefully repairing this wire and its protection in place rather than re-routing it along with the smaller wires along the right fender. The new path would introduce two new engine-to-body flex points. This is no problem for the smaller D+ wire and oil sender wire, as they won't likely cause a fire if they rub through.

But any insulation failure between the blue/yellow wires or the terminal and the brown wire (or red wire) near the starter would cause unintended cranking or latch-up after key release.