Complex sentence: Tom Trana changed to Saab for 1967, which resulted in relative success, including a win in the 1967 Norwegian Rally, until 1972, when he finally hung up his helmet and retired from rallying.
Split into simpler sentences: Tom Trana changed to Saab for 1967, which resulted in relative success, including a win in the 1967 Norwegian Rally. He rallied with Saab until 1972, when he finally hung up his helmet and retired from rallying.