As I said over on rovernet, the biggest difference I think is the coil being on the other fender well. There are also minor differences in how the headlights work, as the 69 shouldn’t support the parking light position. The part in question is called the dash harness, and sadly it runs from the front left of the engine compartment back to the firewall, into the cabin and across the firewall, then back out into the engine compartment and down to the right hand corner. But other than having to take the speedo, glove boxes & centre console out it not terribly difficult to remove. I’d get the burned harness out as a practice run — doesn't matter if you skin a wire or two on that one.
Final though, depending on how badly it’s burned up it may be less work to repair the wires. But that requires quite a bit of electricl skill to do well, and of course it will always look repaired.
Yours
Vern