Need advice help.

I did ask this on my build page but received not hits so I'll ask it here.

Just a quick question about disc brake conversions. I've seen the sticky and get the concept but have a few more questions.
71 > 73-76 disc
The parts I have so far are:
Spindles *2
Backing plates *2
Valve *1
I'll buy the calipers pads lines and rotors from the part store.
I still need to find some upper control arms.
I'm using a 1973 direct connection BB k frame with spool mount engine mounts.
My questions are. Do I now need to buy a new steering box? If so will it mate with my steering colum? I'm guessing I'll need the 73 pitman? Is there anything else I'm missing here? A straight swap would have been txt book but seeing how I'm pulling the 71 /6 k frame and installing the 73 DC big block spool mount k frame things may/are different now.
Advice? Thoughts? help
List of what I'll need-

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