any tips on pulling under dash wiring harness?

on my 74 scamp, I got the engine starting with the key, went to make holes in the new floor to mount the seats, before the carpet, anyway the wiring that runs to the rear lighting is toast, the pink, wire I'm guessing is the main hot wire? as it has all the coating melted off and fused the other wires together, at first I thought I could just unhook it at the connector, yeah right, that pink wire is melted from start, wherever that is, to the last connector in the trunk.
like I said in the other thread, the kid I got the scamp from had a big *** sound system, with 5 leads running from the positive side of the battery, thanks in advance for any tips.

Mark