The car is worth whatever someone is willing to buy it for.

KBB might say $4500, but unless you can find a buyer for that price, it won't sell. Unfortunately, we've had a lot of heavily modified Tiburons sell on our website for very cheap, so odds aren't in your favor. Best of luck anyways.

Posting it locally (craigslist, local automotive websites, local car racing/enthusiast websites) might give you the best results.