Tim Allen is cleaning out his garage. The "Home Improvement" star headed for Arizona on Thursday to sell his 1968 Shelby GT 500KR convertible at the Barrett-Jackson Classic Car Auction. There are 800 vehicles on the auction block through Sunday at WestWorld in Scottsdale. "We are very excited to have someone of Tim's broad appeal and automotive enthusiasm involved with this year's event," auction president Craig Jackson said. The black Shelby GT offered by Allen, a collector who restored the vehicle himself, is one of only 318 built. It is worth about $70,000.