Higher stall converters use a different vane angle/pattern on the pump and turbine of the converter (part of the converter attached to the trans). this means that the pump and turbine require more centrifugal force (read: engine rpm) to get the car moving. What they effectively do it get the engine rpm's higher before the car begins to move, this means that there is more available engine power upon take off due to the increased rpm. I really dont know a whole lot more about the specific changes in vane design. But if you decided to get a high stall converter for the street, say a 3000 rpm stall, this is the engine speed at which the converter will move the car. This isnt to say that you will always have to rev the car to 3000 before it starts to move. The car will move at lower engine speeds, it will just mimic a slipping clutch feeling, if you can understand where im coming from. I would suggest doing some reading on tcs's site or even on howstuffworks so you have an idea of whats going on inside the converter! good luck man
Your torque converter stall selection also depends on the camshaft and other modifications done to the car. Where is your power band? You want the converter to hit the start of power band when you nail the throttle. However, I agree that 2,400-3,000 is a great place to start.
I had a precision industries 3,800 stall 9.5 inch converter installed in my '95 Z28. The car would "free" stall at around 3,000 rpm on the street, when you mash the gas, the car would launch at 3,800 rpm. On nitrous, with the higher HP/TQ output, the converter would stall at 4,400 rpm. When I ordered this converter through PI, I sent them my dyno sheet so that the converter would be a perfect match.