I just ran across this post. I have a '73 K-10 with a Hurst floor shifter. The problem is that it is a generic, one size fits all, shifter. It seems no one makes one specifically for the Chevy 3-speed. It doesn't work very well; you have to shift very deliberately to keep from winding up jammed between gears. If you are going to change out the transmission for a 4-speed I would just wait, unless there is something wrong with your column shift.