I purchased a non-tilt floor shift column for my 70 from a guy parting out the same. This was a couple years ago. I pulled the signal switch and the lock using GM manuals and installed the retaining plate and the cap. When I went to attach the shaft that connects the column to the steering box, I found that the splines on the end of the column were not sticking out far enough to assemble. The parallel grove for the bold was behind the bearing.
I pulled the entire assembly apart. Every detail, inspected it cleaned it and replaced if it seemed worn. Put it back together again, this time installing shaft to the spline before compressing the retaining plate.
I made a tool as shown in the assembly manual that slips over the threaded end on the shaft and uses the steering wheel nut to compress the spring and locking plate.
I tighten it up until it bottoms out and it is still not enough to install the clip that holds the unit together.
I am completely stumped on this one. I guess it is possible that the shaft itself has been compressed due to a front end collision but you think it would be sloppy. Any ideas?
Any one have a disassembled shaft that they could measure? I would hate to go buy another column now but it may be where I end up.
Any help would be appreciated.

I think I'm folling you and I ran into a similar problem on my 70. I swaped out a non-tilt floor shift for a tilt floor shift column. When I went to button up the tilt column, I couldn't get the C clip onto the shaft that hold everything together. After taking the assembly apart and putting it back together a couple times (and spewing a few choice words graemlins/angry.gif ) I went back and looked at my old column and discovered the plate that locks the column when the key is removed had an offset on one column and no offset on the other. I grabbed the offset plate and BINGO, everything fell into place and the C clip snapped on.

I'm wondering if you have the wrong lock plate (sorry - I don't know the offical name of this piece!)...HTH