Fusible links are not oogy boogie. Several are right down at the starter, depending on the year and equipment, where they receive some pretty rough treatment. Eventually they fatigue and die.
According to the bloody PITA to read 1987 wiring diagrams the base optioned V8 truck had three;
-At the 3/8" starter BAT terminal there are two fusible links on one ring terminal. If you replace them use separate 3/8" ring terminals for the wire gauge in question.
--One 2.0mm² (14AWG) fusible link wire protecting the RED 8mm² (8awg) feeder wire to the J-stud pair on the LH side of the firewall inboard of the brake booster.
--One 1.0mm² (16AWG) fusible link wire protecting the RED 3mm² (12AWG) feeder wire that runs to the outside corner of the square bulkhead pass-through plug under the brake booster.
Assuming you have one of the V8 Models and not the L25 V6;
-At the firewall J-studs you'll find at least one 1.0mm² (16AWG) fusible link protecting the RED 3mm² (12AWG) wire that runs to the middle of the bulkhead pass-through plug under the brake booster.
The above only applies to 1987. GM changed the sizes and placement of the fusible links almost every year. Download the wiring manual for your year. Everything is listed on the schematics in black and white.
You can make up links using a 40W soldering iron, ring terminals, electronics grade solder, liquid electronics grade flux, the correct size fusible link wire, and adhesive lined "marine type" heat-shrink tube. Get 60/40 LEAD/TIN electronics solder made with actual LEAD not that no-lead or low-lead ROHAS crap they are trying to foist on us. Lead sticks to copper and tin. There's plenty of other hazardous substances in these trucks to worry about.
Leave the plumbers solder and plumbers acid paste flux in your pipework toolbox it has no place in electrical repair.
Fuses don't have the same characteristics as fusible link wire. They typically blow too fast or too slow. If you only want to make one solder connection you can buy most fusible links from NAPA with ring terminals already installed.
-Belden service replacement fusible links with ring terminals;
--Belden -- 784696 -- 3/8" ring terminal 14AWG Fusible link
--Belden -- 784691 -- 3/8" ring terminal 16AWG Fusible link
--Belden -- 784695 -- 1/4" ring terminal 16 AWG Fusible link
--Belden -- 784692 -- 5/16" ring terminal 14AWG Fusible link
--Belden -- 784694 -- 16 AWG Fusible link with over-molded ID flag and no terminals
