Starter Cable Replacement.

[Spool]

Hey Guys.
73 C20 Here.

I have a starter cable that is acting up and needs to be replaced.

Basically I need to narrow down what the cable is and it's connections to replace it correctly and am a bit confused.
I took a few pictures into a diagram to help make sense of it but does anyone know where I can pick this cable up or if it has a specific name?

It goes from the solenoid, splits off at the alternator, continues to distributor and splits off again to (a power supply? and the back of the fuse box?)
Between the distributor and the back of the fuse box there are 3 lines, 1 with an inline fuse.

Can anyone help me make sense of this? The service manual doesn't get into wiring diagrams, which I just ordered today.

[bd]

Have you studied the 1973 Wiring Manual?  That section of harness needs to be fabricated as needed or procured from a wrecking yard.  What seems to be the problem that you need to correct?

[Spool]

Not yet no, I just ordered it as I'm not crazy about PDFs and Kindles.

The issues seems to be a short. But the cable is also in terrible condition.

Once in awhile the truck fails to start. When I jiggle the cable, I hear the heater blower kick on and boom, she starts.
Connections on the starter are tight, but the cable is crap. Plus as a project truck, fix one thing at time, why not replace the 44 year old cable with a new one?

Why go to a yard? Nobody carries?
Would I be able to cut and splice on the connections myself if I were to replace the proper gauge or is that more work than needed?

[bd]

I doubt you will find that small harness as a standalone component anywhere, brand new.  Fortunately, fabricating a replacement harness is not difficult, though I highly recommend that you have the factory wiring diagram in hand and carefully studied, before you begin the job.  The symptoms you describe sound like a damaged fusible link or loose/burned wire terminations.  You may not need to replace the complete harness to restore proper function.  As part of the discovery stage, make some voltage drop tests and closely inspect the red B+ feed wires in between the starter solenoid battery cable stud and the firewall junction block.  Give the three fusible links (two at the starter and one at the firewall junction block) a stout tug to see if any stretch or separate.  Inspect the wiring and terminals for visible evidence of heat damage (darkened, brittle, distorted, or blistered wire insulation, annealed wiring or discolored terminals).  Determine the actual cause of the symptoms if you can, and then perform the repair with that knowledge.

Make a photocopy of the schematic on which you can write notes and color the various wires to make the job a little easier.  Doing an optimum repair requires appropriately gauged SXL/GXL primary wire in the original factory color(s), 6" long pieces of fusible wire sized to complement and protect the new B+ primary wiring, bare ring terminals, 60/40 or 70/30 rosin core solder, some marine grade heat shrink, good quality electrical tape, high temperature convoluted loom, a soldering iron, a decent pair of wire cutters/crimpers, and a wire stripper. 

FYI - the two inline 4-amp fuses are part of the instrument cluster ammeter circuit and should be left intact as long as the wires are not compromised.  Since the ignition has been upgraded to HEI, the yellow wire between thew starter "R" terminal and the distributor should be eliminated.  More Q&A with details supplied as the repair progresses.  First, discover the actual cause of the failure and familiarize yourself with the factory wiring using the OEM manual.

[Spool]

Thank you for your time BD, I really appreciate it.

I'll be testing the voltage drop first as you mentioned.
Found a nice video to help me grasp this all a bit better as well. https://www.youtube.com/watch?v=WMXENKujYtc

Questions if I may?

1.Red B+ cable = positive battery connection to starter solenoid?
2. Which cable to the firewall junction block? The junction block is near my heater blower correct? (The top left of my attached photo?)
3. Lastly you mentioned the two inline 4-am fuses. What are these?

[bd]

1. Red B+ cable = positive battery connection to starter solenoid?
2. Which cable to the firewall junction block? The junction block is near my heater blower correct? (The top left of my attached photo?)
3. Lastly you mentioned the two inline 4-am fuses. What are these?

To be sure, our discussion would make a lot more sense if you followed along in the wiring manual.

• B+ refers to constant source power in a direct current (DC) negative ground system.  Depending on context, it can mean "Battery Positive" or it can mean "Bus Positive."  Within the context of our discussion, B+ simply means "battery hot" or constant 12.6 volts.  Any cable that provides constant 12.6 volts to a point of distribution is referred to as a "B+ feed" or "positive bus."  Essential examples include the battery cable, as well as the 10-gauge red wire that connects to the starter solenoid 3/8" battery cable stud through a fusible link and then runs around and up the back of the engine to the firewall mounted, two-post junction block where it connects to the alternator output stud through a second fusible link and additionally runs to and through the firewall bulkhead connector into the cab.
  
  
• Correct.  The plastic mounted, two-stud block labeled "Power" in your collage of images.
  
  
• The ammeters in the 1973 - 1975 model GM trucks were shunt or bypass gauges.  That is, only a small portion of the total current moving between the battery, charging system and chassis actually passes through the ammeter.  The two inline, 4-amp fuses are located in both circuit connections to the ammeter in order to protect the ammeter coils and small gauge wiring from over-current damage in the rare event that the 14-gauge fusible link at the starter melts open or the battery cable connection to the starter loosens and the alternator begins to charge the battery through the ammeter circuit.