You can use a threaded shaft that is cut and using a clutch nut. If you use a SG shaft then you wil require a sq nut.
~ Jon
EDIT- the OS CVX - S 15 is the one you want . The "S" stands for short as in short shaft. You are limited in engines but there is a plethora of styles with a threaded shaft. I know people use the MT12 on ST and they are great. The 15 size engines are great for torque but there are some exceptions on the 12 size.
~Jon