200-4R transmissions and 1982 / 1983 700R4 transmissions have a 27 spline input shaft. Vary few early 1984 700R4 transmissions have a 27 spline input shaft. All 4L60E transmissions through 1997 have the same 30 spline input shaft as 1984-1993 700R4 transmissions. 1998-2000 4L60E transmissions may or may not have the same input shaft as a 1984-1993 700R4 transmission. This torque converter will not work with a LS type motor, except a C5 Corvette will work. The 1200 and 1400 stall speeds are for Diesel engines.
Pump pressure drives the impeller hub into your transmission pump causing the pump to fail.
It also creates bearing endplay creating premature converter failure. When the converter balloons, it loses the dynamic flow through your converter, resulting in loss of efficiency and horsepower.
Anti Ballooning flanged hubs keep the converter from expanding outward. The converter will actually become longer from front to rear when it balloons.
This is just another of the many things PATC does to their converters to make them stronger.