Here is another thing to consider, insurance companies base values on publications from Kelly and NADA. A quick check at kbb.com shows that they don't publish values before 1994, and nada.com shows a low book value of $1100, and a high value of $2975. That high figure is for a vehicle in PERFECT condition. Anything can lower the value, faded paint, worn tires, dirty engine, parking lot dents (little small ones), collision damage, the person doing an estimate having a bad day(don't laugh I've seen it happen), almost anything can and will change the value. Another thing to consider, a dent the size of the palm of your hand is about $500 to repair, make it bigger, it will cost more to repair. When dealing with insurance companies, all bets are off, some of will total a car simply because they don't want to deal with the extra complications of repairing an "old pile of junk" (no I am NOT saying that yours is a pile). There are a lot of variables, a lot more than there is room to put here.
The best advice I can give you based on 16 years of running a body shop, if your dealing with an insurance company and you don't like the way they treat you, get an attorney.