A trade association will soon adorn gas pumps across Indiana with ads opposing a Republican plan to use higher fuel taxes to pay for infrastructure repairs, a tricky sell in a conservative state much more accustomed to cutting taxes than raising them. The ads at gas pumps, filling stations and convenience stores will include the contact information for state lawmakers, a hardball tactic urging motorists to voice their opposition to the plan that would raise fuel prices by at least a dime a gallon.