[Macroni]

There is the concept of diminished value. I have no idea how it works but I am sure your insurance agent/broker should be able to provide assistance.

The undocumented nature and quality of these repairs should be of greater concern. My recommendation is to take the car for inspection at a body shop that is fluent in the type of repairs required. Get an estimate for proper repair. This would become a further deduction after diminished value.

The purchase math should look like this:

Value of 89 Turbo Retail [40,000 miles/fair condition/ Kelly Blue Book:$27,000 (IMO a low valuation for a 40k car)]
minus PPI mechanical deductions
minus Diminished Value
minus Body shop repair estimates

Your Purchase price.

The wholesale value on a fair condition 40000mile car is $17,800 per Kelly Blue Book.

I believe the proper advice on this car is "Run Forest Run"