All the standard capacity Whirlpool / Kenmore belt-drive agitators are interchangeable. The bakelite Straight Vane, the two bakelite Rotos, the plastic straight vane and Super roto, the Roto-Flex, the Vari-Flex, the Dual-Action, and the Surgilator all use the same agitator shaft length, and are fully interchangeable, given the use of a drive block for some.
Even the Penta Vane and Swirl, the large cap. Dual-Action, and the Double Duty Surgilator (with the wings) are the same height, and would install properly green machine, because washers using these agitators use the same transmission shaft length. The top of the agitator shaft simply does not rise as far out of the basket on these models.
It is ONLY the 1968-1973 Kenmore 18lb. machines and their Whirlpool counterparts (may have started as early as 1966) which used the tall shaft transmissions which can utilize the large Super Roto-Swirl and the tall Surgilators.
Gordon