Those "giveaway" cars are part of Auction America's Auburn, IN event. Home of Auburn/Cord/Duesenberg museum. Here's a link to the website for the auction.
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The cruise goes from Pontiac, MI all the way down Woodward Ave to 8 Mile Rd in Detroit. Here's a quote from the link below:
"WDC takes place along 16 miles of Woodward Ave through eight communities in metro Detroit: Berkley, Bloomfield Hills, Bloomfield Township, Ferndale, Huntington Woods, Pleasant Ridge, Pontiac, Royal Oak. The 16 mile cruisin loop is from Ferndale on the south end (north border of Detroit) to Pontiac on the north end."