if you've got the original 67 steering setup on the car, it should look like this:
http://www.67chevyii.com/referenceimages/steeringbox_oncar.jpg
there is a small clamp that holds the end of the steering column onto the steering box. It's not really a "rag joint". It's just a female 36 spline input on the box, with a 36 spline shaft from the column. The input has a gap that the clamp squeezes to force it to grip the column's output shaft. Loosening this clamp, disconnecting the pitman arm, and then removing the steering box bolts from the frame should let the box fall free.
sometimes the steering column to steering box spline joint gets sorta gummy, so you may have to work at it a bit to get it to drop, but it will eventually.