The dollar powered its way Thursday to one of its best days in months, as a very strong manufacturing report pushed stocks higher and forced many currency traders to cover bearish dollar positions. After exiting 2002 on a whimper, the U.S. currency began the new year with a loud bang, reversing many of its recent losses. The Institute for Supply Management said its December index of manufacturing activity moved to 54.7 from 49.2 in November, snapping three straight months of contraction. Economists had been predicting a reading of 50.0. Any reading above 50.0 indicates expansion of activity and prices in the manufacturing sector, while readings below 50.0 indicate contraction. The index was 48.5 in October and 43.6 in September.