As mentioned above stock converters for TH350 were about 1800 rpm, but there is never an exact number as many factors determine stall and they get a little loose with age. I was always taught to start the car, with the brakes applied so the car will not move, place the transmission drive, open up the throttle, the engine will accelerate to some rpm level. This rpm point is called the stall rpm, and it's determined by two things the torque that the engine can make at that rpm and the converter slippage. So 2 different 400 with the same converter can stall at different speeds.
