88 735 6 speed - insurance wants to junk it...

I have a 1988 735 six speed manual (which I know is rare here in US). I've been restoring it for some years now - it runs great - just rebuild the front end and was on the way for rear struts when hit.
Insurance accepts liability but won't pay the full amount estimated - $3400.
Damage it to the body panel between trunk lid and bumper. I believe the bumper is straight, just had its plastic mashed.
Since this is my main car which I use for work (only 200 miles per week) and since I want to keep the car, not salvage it, I need to show AAA that this vehicle is worth that amount of money.
I can't find any useful info on the net as of yet - last one for sale I found was in 1910 and guy wanted $9000 - probably a tad high
I saw another for about half that.

Can anyone steer me to a good valuation source for this car?

Thanks
jg