Walworth, WI -- Mecum will return to Kissimmee’s Osceola Heritage Park for its Aug. 27-29 Summer Special auction featuring approximately 1,000 vehicles.Photo: Mecum AuctionsThe auction lineup will be highlighted by the 14-car collection of auto enthusiast Marty Nelson that features a restored 4-speed 1968 Chevrolet Camaro RS Z28 and a...