i have one on mine, what i did was cut a peice about 2 inches in length from above the ball, lowering the knob down, and then cut and welded the 2 inch piece in below the ball, so i have a really short shift now, too short in fact, if i were to do it again i wouldnt have taken any off above the ball as it doesnt really make that much differance and puts the stick in an awkward position, putting it below the ball makes all the differance really.
if you want to do what baz said and use the standard knob, the thread is only m8