I have tried using the GM torsion tool, 3 different two jaw pullers and I still can't get the new key in.

 

Unbolt the upper shock nut, and disconnect the sway bar end links. This will allow the control arms to droop and should take a lot of the load off of the torsion bars, making it easier to use a puller. I personally use a strong c-clamp whenever I do mine. If you want to take more of the load off of the torsion bar, disconnect the upper ball joint from the spindle, just make sure you support the steering knuckle somehow to keep it from flopping around and destroying your lower ball joint.