Getty Images / Cliff Hawkins David Portnoy’s Barstool Sports could drive “rapid share gains” for Penn National Gaming and help drive shares 20% higher from Wednesday’s close, according to Goldman Sachs. The research firm initiated Penn National at a buy with a 12-month price target of $60 on Thursday, arguing that Barstool’s massive social media following can help lower customer acquisition costs for Penn National. In January, Penn National bought a 36% equity stake in Barstool Sports for $163 million, and has the option to acquire another 14% stake in the economy via warrants three years after the deal. Since