wiring harness specifics, what AMP fuse? 1987 K5

[hatzie]

Fusible links are ultra slow blow fuses that are more difficult to replace than fuses by design... for lack of a better description.
They have a specific design purpose that they are uniquely suited for.

What Am I saying?
They are time consuming to install on purpose. This forces the owner to discover what's causing the large current draw instead of slapping a larger fuse in place and eventually setting fire to the vehicle. This is not the main purpose of using them just a happy side effect...
These circuits also usually contain "high inrush current" devices like tungsten filament lamps and electric motors that draw significantly more power on startup than they do while running. Alternators fall into that category as well since a fairly depleted battery sucks up a big slug of current when charging starts before nearly instantly settling at a lower charge current. Look at your battery charger analog Ammeter needle. It swings high and settles down lower almost instantly when you switch on the charger.
Those large inrush currents will burn out regular fuses after several (10-30) cycles and circuit breakers don't like it either if they aren't rated for electric motor duty. Fusible links can be rated a lot closer to the running current of the attached devices without being overly stressed by a second or less of high inrush. This way when the circuit starts to draw more current continually than it should it will burn up the link rather than the attached wiring harness or device.