70 up charging system upgrade question

Ok pulled red"batt" wire out of connector. Here is where it leads to...one of the infamous splices. 5 wires(1red batt, 1 red/white tracer, 3 black( hl switch, 1 to P in bulkhead and other WAS to ammeter(bypassed)...down the rabbit hole lol
Wires are pretty brittle I wonder how deep I gotta go to replace all the switch wires....
Splice circles in hm drawing and in factory schematic.