So take a piece of plywood and lay out the original harness - with everything labeled. Some guys posted pictures in the FABO thread called "Wiring Nightmare"
Then lay your new harness out next to it. Use the new as the base and make it match the original., Copy and Add/transfer wires as needed.
Or maybe do it the other way around. Use the original as the base. Transfer in new replacement wires from the new harness. Then do the remaining ones as needed. Some loose zip ties will keep them bundled after removing the tape.
Once the tape is off the original you'll have a better idea of condition.