Pick your battles carefully. It can be done. Will it be reliable? That's another story.
I've repaired terrible hack ups on far simpler engine and chassis harnesses. Then I repaired one or two splices again after a year or two of service and a few more as time went on.
Solder joints will make the copper brittle. Field installed crimp splices fail in interesting ways too. Neither splice method will flex like the original unmolested wire.
If you're attached and employed it's not a good use of your time... or your woman's patience.
Find an LS harness that isn't hacked to pieces by the
yard monkeys. Then carefully label and pull it yourself. Lay it out and carefully strip it down to the essentials.
That 70 year old guy prolly has a good supply of patience. You'll need some.