Determining a value... and price that I should pay

[Snibble]

Hello..

I need some assistance in knowing whats a fair/good price I should offer in a vehicle.

Its a 1989 560SEL black exterior gray interior..
It has sheepskin on the front seats, seats are in very good condition, only fault is a 2" wear spot on the driver's bolster from seat belt.... but its not bad.
back seats are perfect.
trunk is immaculate, has spare with lots of thread and jack.
the paint has been recently repainted, not the best job... a 7 of 10 on the hood.. 8 of 10 everything else. Its been colored monotone. looks like new from 5-ish feet away.
Suspension system is good
engine has 202,000+ miles on it, has many new or newer parts on it.. however the engine mounts are shot. There is some oil leaking from it too, but not too much. Engine drives strong.
Car has 16" chrome lorinser replicas.
Chrome on car is very good.
AZ car, clear title

I need a "shell" for a M119 transplant, so the engine and transmission will be out. The owner is really a curbstoner.. and is desparate to sell. He had it for $3300.. but lowered his price to $3100. There were a bunch of people that came to look at the car, too.

With the above description... what would you consider a fair price or what I should offer to him?

thanks in advance