One of the weaknesses of any old unibody car is rust. If the buyer describes it as heavily rusted I tend to mentally upgrade that to "terminal basket case, use for parts". I wouldn't pay $500 for a parts car. I'ld say around $200 is closer to the mark _if_ the drivetrain and interior are really good and usable to you, $100 more if it has a good overdrive transmission. If either are so-so, think closer to $75. Otherwise just pass it up and look for a better one. Interiors are easy to swap and with minimal work you should be able to fit a 240 interior and get better seats as well. Mechanical parts are cheap and plentiful, they were used on anything from the amazon through the '75 240.

Bram