Just went to check KBB for you. For a 1988 325is, 5MT, 190k milage, "good" condition car the price was around $1,600. The reason I used 1988 is because it only goes back 20 years in their database. So 1987 isn't an option. Based on this, and the actual condition of the rest of the car (minus AC) I'd probably offer $1,500 and go from there. Might help if you went to
www.kbb.com yourself and printed out the page on the car that I just found.
Here is a screenshot for you.
