If you're shooting Right Shift, Centered, and Left Shift with the camera stationary (i.e. flat stitching) you can probably even stitch the images as layers in PS without a pano program, since no projection transformation is required.
Here's a good blog article:
Ideally you could use a focusing rail mounted sideways to adjust for the lens shift offset. I'd get one that has a scale in mm so that you can dial-in the exact shift amount used on the lens (±12mm).
Happy Photomerging,
Todd