The "Bloomington Gold" event in (Bloomington) Illinois is probably closer to Indiana than Bowling Green. This event is the "Pebble Beach" of Corvette events. Your friend can likely get just an accurate valuation there as he would in WI.

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2009 ML350 (106K) - Family vehicle
2001 CLK430 Cabriolet (80K) - Wife's car
2005 BMW 645CI (138K) - My daily driver
2016 Mustang (32K) - Daughter's car