[ckhd]

OK, I'm going to start with the last thing first: Yes, in '67 the steering box was the same. They had a valve that attached to the box to control the steering ram. This is only important if you are going to install OE style power steering with a hydraulic ram. You specifically said "later style saginaw", so it doesn't apply.

The frames are different. Most people dimple the frame so the newer saginaw style lines up. Some less safety conscious people use spacers. The holes are also different. Be prepared to drill.

The rag joint isn't what's different. The shaft from the steering column to the steering box is different. In 69-72, it has a swivel type device up at the column that allows for the different position of the steering box. In 67-72, the shaft is solid. The reason you want to worry about this is simple, fatigue. If you don't change out your '67 shaft, it will fatige and break. Probably while you're going fast on a windey road.