The 76-year-old - who is nearing a half-century in charge of the company - predicts sales of new and used cars at his outlets will jump 17% from 150,000 to 180,000 during 2004.
Clark - who was knighted earlier this year - will enjoy a large boost in his personal fortune, which is currently £315million, making him Scotland's 12th richest man.
He told the Glasgow Evening Times, Scotland's biggest private company has cashed in on car makers cutting prices, and historically low interest rates.
Profits are set to soar from £44m to more than £60m in the year to December.
Turnover is predicted to jump 13% from £1.47billion to around £1.65bn.
Clark, who is chairman and chief executive of the firm, said recent interest rate rises had 'no drastic effect' on his business.
He says: 'Interest rates are still at historically low levels and we're still selling enough cars.
'It's not been easy to bring the business to this level - it's been nearly 50 years in the making.
'Our strategy is to buy a loss-making property from a rival and turn it round until it makes a profit.'
The debt-free firm has £30m in the bank.