United Auto Workers President Dennis Williams, whose union indirectly controls the largest single block of General Motors Co (GM.N) shares, told Reuters an investor group’s proposal that GM buy back $8 billion of its stock is premature, and the amount too high for the company’s long-term health. An investment firm controlled by Harry Wilson, a former member of the U.S. government task force that restructured GM through bankruptcy in 2009, together with four other hedge funds, is urging it to return part of its roughly $25 billion cash trove to shareholders.