Ohhhhhhhhhhhhhh.....a dealer car. Was he an Alfa dealer? Or what does he sell new?
You have a lot more room with a dealer. He wants to sell the car.
Find out the history of the car, if he's serviced it, you should be able to see all records. If not, raise an eyebrow but not much else.
Find out what the PO traded for and how much they gave him for the Alfa. He might not tell you, but it's the type of q that shows you're looking at this logically and not emotionally,. Emotions=impulse buy.
Repainted? Body work? Why wasn't the hood weather stripping replaced? Look at door jams and see if they're the same color and consistency as the body. A well kept 35k mile example should be wearing it's original paint. Check the body carefully.
Typically if the radio is changed, a good system is put in. If not, it says something about the owners willingness to spend. Frankly after you buy a Spider and take out the **** resonator you'll never listen to the radio anyways. But still.
Don't show your emotion. At best this is a $15k car, dealers always mark it up to negotiate down. See if they can add an extended warranty, which you should seriously consider demanding if the price stalls.
'89 Spider Quad, "Rosa", original owner..still in love all these years...