Is this worth $17,000?

http://www.racingrides.com/ad_details.php?ad=97

What should I offer him?

Cant judge what it's worth by one picture. Look at it in person before you make an offer would be my advice.

The drive train is worth $$$. A BB isn't cheap. A crate engine from GM is selling for around $7k (454).
Get rid of the wheels & put some factory rims on it & it will look nice.

Check mine out.