What Cam should I get?

More of a 4spd manual guy talking here, but;

A stall speed is a suggested area,,,, and a grey one at that,,, of where the converter will apply the power in force. The more torque an engine makes the high the stall will be for that converter.

A car will move even if you pop in a 5000 stall converter because it is moving fluid through the trans. But it is super inefficent and will require more pedal to move foward. The amount may be slight to move by compare to a stock converter, but the faster you want to go, the more pedal will be needed.

You need not warm up the converter but the engine and tranny should be at proper/best working temp.
Holding the foot on the brake and reving up the motor will bring you closer to the stall converters working point but probably not get you where you need to be exactly. At the flash point, which is where the converter comes in and surpplies the best result/effort in car movement, is best achieved with a trans brake and will reduce E.T.'s and make the acr more consistant in the 1/4.