Markings on converter

There might have only been 3 different physical sizes but the internal fins were set at a different angle to produce a different stall speed. Therefore there were different stall speed converters for the same engine in some cases such as a 383 vs. 383 magnum and 440 vs. 440 magnum. I have owned cars with each and you could definetly tell it wasn't just derived from the higher torque output. BTW: physical size has very little to do with how much a converter stalls.