Getting guaranteed car sales data for Spain is difficult. From what I did find, the market back in the 60's was limited to brands made within the country. In 1961, less than 70,000 cars were sold so not a market big enough to support many manufacturing plants. Sales grew well and by 1969, perhaps 380,000 cars were sold.
Below are the sales as accurate I could get for 1969:
1 Seat 222,000 58.8%
2 Renault 73,000 19.4%
3 Simca 28,500 7.5%
4 Citroen 22,500 5.9%
Others 31,800 8.4%
Some may wonder about the brand Seat - pronounced 'say - at'. Well, when the Spanish government decided to have a local brand, both Fiat and VW sought to be the alliance partner. Fiat won and by 1950, the first Seat cars came off the assembly line. Then a falling out in the early 1980s between the Spanish government and Fiat led to Fiat leaving the venture and VW quickly moved to replace them.
Today, Seat fights with other brands for market leadership and its share is about 9%. The Spanish car buyer has plenty of choice in the car market now. No one brand can command even a 10% share, quite a unique situation.