NEW YORK - Sales of U.S.-made cars soared 24.4% in October from a year before to a record monthly high of 1.73 million vehicles due to aggressive campaigns by makers giving interest-free loans, a research company and carmakers said Thursday. The good showing followed a 9% decline in September following the Sept. 11 terrorist attack on the United States, according to Autodata Publications Inc., which compiled figures for U.S. automakers and foreign makers operating in the U.S.