Bob Jenkins, longtime racing announcer and former voice of the Indianapolis 500, dies at 73 from ESPN News Services and from YardBarker.com/www.yardbarker.com: Longtime racing announcer Bob Jenkins, a former radio voice of the Indianapolis 500 whose career spanned more than five decades on the Indianapolis Motor Speedway Radio Network, died Monday at the age of 73, Indianapolis Motor Speedway said in a statement. Jenkins revealed in February that he had been diagnosed with brain cancer and planned to scale back his work at the speedway as he underwent radiation and chemotherapy treatment. Jenkins, who survived colon cancer in the 1980s,…