Torque Converters??

This might help with the idea:

John Kunkel:

OK, here is the factory stall speed specification for all 727 converters, direct from the '70 service manual:

Engine Diameter Engine RPM

225 10.75* 1450-1650
318 10.75* 1750-1950
340-4 10.75* 2250-2450
383-2 11.75 1850-2150
383-4 10.75* 2350-2650
440-4 11.75 2000-2300
426 2X4 10.75 2650-2850

Notice there are only two size converters, there was no high or low stall.
*The identical same part number converter is used on the 225, 318, 340, and the 383-4 but notice the difference in stall speed.
The stall speed of the converter rises with the power input, it's that simple.