Gears or torque convertor

My two barrel cuda spun the tires even though they where crappy tires, were all assuming his car pretty stock if so wouldn't a converter change have little effect with out more done to it like cam, exhaust and gear? Why the choice is it budget? do cam, converter and gear it will make a big difference, my buddy's duster was a 4 gear 318 with 340 top end with headers and the swap from 3.23:1 to 3.91:1 made the hughest difference went from a fast car to an animal.