Just shorten it at the bottom and install a bearing in the bottom of the tube to support the shaft. Leave the shaft long enough to file some flats and install a DD u-joint.
thats what people do when they install a power box or rack and want to keep the stock column, but he wants to keep both the stock column and the box but shorten it. I vote for cutting a Z into the shaft, having a professional welder (either yourself if qualified or someone else), weld it back together, than welding a sleve over the cut and so on.
