By John S. McClenahen There's the possibility that U.S. GDP growth during the second six months of this year may be stronger than now anticipated. That's one conclusion that William Dunkelberg, chief economist at the Washington, D.C.-based National Federation of Independent Business (NFIB), is drawing from the highly optimistic results of a survey of small business owners. The NFIB Research Foundation's Index of Small Business Optimism registered 104.7 in August, its highest level since monthly surveys of business conditions began in 1986. "The very good news was improvement in capital spending plans, inventory investment plans and hiring plans -- all a real plus for second-half GDP," says Dunkelberg. "Job creation will turn positive over the next month, finally. Capital spending is picking up, slowly as expected, but the direction is good. Inventory accumulation could turn aggressive, adding some real energy to manufacturing and to the GDP math."