As near as I can tell from the harnesses I've disassembled the wires are all in the harness for any of the 15M-based BB's of the day. Some of them put the wires in different connector holes, which makes a drop-in iffy -- you have to pin-out the wires and sometimes shift them in the connectors to be sure they're where you need them for your bike. If yours are melted in a big lump, tracing wires with a meter isn't going to tell you much. Unfortunately, harnesses and paper diagrams don't always match either -- simply following the map can have bad results.
So the best way to replace your main harness is to have the replacement, the old harness and the bike in the same place. That doesn't sound like it will happen. The next alternative would be to send your melted center section along with the proposed replacement to someone who can make really good guesses about the pinouts, a sense of humor about wire, and either the lack of ability to feel pain, or a whole lot of patience, and have them make the necessary (anticipated) pin relocations.
That someone would be me. PM with a ph# and we can chat about where to go from here.
