heres my take on this
from looking at that article, and it saying that it works on older style manually controlled automatics(no computers) that this must use an actuated rod to physically change the gear the transmission is in. It doesn't give the computer a signal or anything to change gears
it would be just like moving the shifter on the console....
I don't think you could get a seperate 3rd gear shift and 4th gear shift as the SHO is not setup for that, you have 3 forward gear detents, D, 2, 1... with you having an overdrive off button to control that department... if you started a run, with the overdrive button off... then you could get it to go 1-2-3 and hold out 3rd... to shift into 4th you would have to press the button on the console shifter....