Kemosabe, most of us have worked fire jobs and we know what you are talking about. tshea called it right, the local AHJ will be the ones that determine if the KAT must be replaced. The Natinal Electric Code would allow the old wiring to stay if it's safe but that does not mean the local authorities will. The electrical contractor that does the repairs will have to get a permit to change the panel and they should have a good idea of what the local authorities will accept. Most homeowners want a new house if they have a small fire but they don't normally get it. One more thing is finding a local contractor to do minimal repair work. If I think a job is dangerous I'm not going to put my name on it. I would suggest getting estimates from a local contractors. It's impossible to make a decision about a job without seeing it.