As everyone said, the trans gear ratios are just as important.
My car has a stock carb'd 302, with a T5 trans. When I bought the car (it was already built), it had the stock 2.73 Mustang gears in it. It was dreadfully slow in 4th gear, and 5th was useless below 75 mph. I put 3.73s in the car. Yes, 1st gear now winds out pretty quickly, but I like the acceleration it gives (I have sticky 275 17" tires on the back, so wheelspin isn't much of a problem). 5th gear is now useable, and I can cruise comfortably on the highway all day long. But my 5th gear is a big overdrive gear. If you don't have overdrive, you may want to think in the 3.27-3.50 range. I'd go for 3.50 just for the extra kick when you hit the pedal. You'll also find that the 3.27s and higher will really lose acceleration in the high gears. Even now with my 3.73s, my acceleration in 4th and 5th isn't what I'd call supercar fast. Damn aerodynamics!
Steve