I agree with those that say try to get the $7300 and the car. You seem to love this car and I'm sure you can put it right for that...but remember it will have a Salvage title.

If you can't get them to give you the car, unfortunately you may need to face reality on how much your car is worth on the market. NADA is completely bogus. The later year 450s are considered the least desirable of all the r107 SLs. With carefull shopping you can pick up a 560SL with similar miles for $10K, I recently bought a '73 450SL (good year) with 101K miles for $4K (needed $2K in work from sitting, so $6K to be top condition). So if you can't get them to give you the car I'd shoot for $10K.