If you think the top end is ok then it should be. The low speed needle is what needs to be turned out (more rich) because it sounds like there isn't enough gas getting to the engine to get it rolling. The low speed needle is on the side of the carb. if you look where the throttle linkage connects to the car...look to the side of that and you should see a little screw. Try and richen the low speed needle because if the top end is ok but may be a little lean richening the low speed needle will give the engine the gas it needs to get to the top end. Also, here is a link that will tell you everything you ever wanted to know.
Engine Tunning