LOS ANGELES — For years, the Rose Bowl has walked the precarious line between tradition and technology, striving to keep up with modern-day venues while maintaining the nostalgic touches that make it a national landmark. Get ready for one of the most dramatic changes in its 103-year history. The stadium is undergoing a major overhaul of its south end — the one facing the San Gabriel mountains — that will transform 5,000 underutilized bench seats into a field-level club featuring slightly more than 1,000 VIP seats. The transformation is expected to be finished in time for UCLA football’s home opener against San Diego State on Sept. 12. “We honor the past, but we’re going to continue to move into the future,” said Jens Weiden, the Rose Bowl’s chief executive officer. “We never thought to stop this project, no matter what came up.” Last October, in the wake of UCLA’s threats to terminate its contract with the stadium, the Rose Bowl Operating Co.…