After surviving the heat, dust and potholes of South Asia, 75 vintage cars rumbled along smoother roads across Iran on Monday in the second Beijing-to-Paris car rally. After a rest stop in Isfahan in central Iran, the drivers hit the road again Sunday, cheered by hundreds of Iranians lining the streets. “The roads here in Iran are wonderful, and the people are great,” said Ray H. Carr, a hardy American millionaire who at 73 predates his vintage auto, a gleaming green 1939 Ford Deluxe. The drivers plan to reach Paris on Oct. 18. after covering 10,000 miles and 11 countries in 45 days. The event commemorates the first transcontinental rally from Beijing to Paris in 1907.