The 1975 Southern 500 was a Winston Cup (now Nextel Cup) event held at Darlington Speedway on September 1, 1975. Bobby Allison won his third and final race of the year, leading 119 of the 367 laps in route to a 25-second victory on points leader Richard Petty. Petty continued to expand his points lead, holding a 657-point lead on Dave Marcis (24th-overheating). Stats