Stall speed is directly related to load and engine power. For example, let’s say you have a mild big block making 425 lbs ft of torque. The rear axle ratio is 3,08 with 35 inch tires. And the B&M converter has a max stall speed of 2800 rpm. Take off the 35 inch tires, install 28 inch, the engine load is now lower, that drips the stall speed to 2600. Put the 35 back on, swap the mild big block for a torque monster 540, now the stall speed might be 3000. Get rid of the 3.08 gears, bolt in some 4.10s, now the stall speed is back to 2600. These are all just speculation, there is a bunch of science in converters. That’s why I suggested a custom converter, who knows exactly what a off the shelf converter will do.