Some great advice for tracing.

I find it much easier to work with pictures and diagrams.
Feel free to download any of the diagrams off this page as starting points.
http://www.heritech.org/cuda/Charge.html
Modify it to match your 71, or do your own from scratch using screen shots from the shop manual. You can see I did that for my '67 (at bottom of page linked).
MS Paint will do pretty much everything needed.

Why?
This will be easier to figure once you've ID each damaged wire.
The wire that should have protected all the rest from too much current from the battery is the fusible link.

A rodent chewing partially through the Battery + to Relay would reduce its current carrying capicity but wouldn't explain the damage at the bulkhead and behind the dash. A connection to ground (such as bare wire touching the body due to chafed insulation) would draw as much as the battery can deliver.

If you're going to replace individual wire yourself, you'll need:
Packard 56 terminals for a range of wire sizes.
Small flat terminal removal tool makes it easier.
A good crimper - Compound action and exact fit makes it easier.
A good wire stripper.
Electrical contact cleaner.
Correct wrap - or the wrap of your preference.
Wire with the correct insulation. I like to go to the marine supply because they stock many different colors and sizes that can be purchased by the foot. Also know that most wire at auto parts stores are for chassis. Engine compartment insulation has better oil and heat resistance.

That's all for later, if you go that route.