You really should look at the Shop Manual. Not just the assembly instructions linked above.
The outer column will come off the shaft too.
If you need to separate the box from the shaft you will need to dissassemble the steering box. You should look at the Shop Manual, this is like taking a watch apart.
If I recall you will have to remove the large nut on the end of the shaft- in the steering wheel. The internal shaft dose not remove from the steering box. The stock column carries a lot of raod noise and vibration into the wheel not to mention it's dangerous in a head on
On the stock setup everything comes off from inside the car and you end up with a shaft sticking out of the floor, in order to remove this you either remove the whole steering box through the bottom or cut the shaft, cutting the shaft is OK if you are converting to a 605 setup because you will end up using a rag joint on that installation and there are several ways to accomplish that conversion. Hope the info helps.
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