The booster is easy, the bracketry is where you have to choose a path and follow it.
You have a few options:
1) Take a look at the parts board and see who is parting out a 71 or 72 C10. Ask for cost of whole power brake setup (brackets, booster, hoses, manifold vac fitting, master cylinder, and lines from the distro block to the frame blocks. Get as much as you can, this will increase the bolt-in aspect). Swap it in. Note the lines from the distro block are further forward, so if you don't grab those, you'll need to bend your own or buy new. They aren't expensive, even pre-bent, so don't worry too much about that. Keep in mind that doing this runs the risk of getting a not-so-new/possibly defective, at the very least "crusty" parts. Parted trucks are just that, and they are usually very crusty - BUT, they are original and correct GM, so perfect for a survivor - you can clean and test the parts as you go, and buy new if needed. So, even if you do this, be prepared to get some new parts. Bottom line, you need firewall booster brackets, pushrods and stuff all the way back to the brake pedal, master cylinder, rod between master and booster, and lines between the master and frame-mounted fuel blocks. I'm probably missing something... I THINK your distrib block will still work correctly because it is disk/drum in 71, but if they'll throw that in, I'd grab it also just in case.
2) do same as above, but JUST get the bracketry and push rods (this way saves money on the initial GM parts buy from a parter outer). Buy a new booster for a 71 C10 and a new master cyl for a 71 C10, and some new distro block to frame lines (or bend your own).
3) buy a booster bracket from member CaptainFab - and take his recommendation for a bolt-on new booster to add to it. You'll need to generate a few custom parts - like tailor your booster pushrod length (I think... might ask the good Captain). His brackets look awesome and tuck the master cyl back onto the firewall, they don't stick out nearly as far as stock bracket system would.
4) Talk to member PICKMUP. Frank puts together some BEAUTIFUL setups - firewall to distro block, all new parts. Worth the very reasonable price and top quality. This may be the least work approach
You'd probably only need to buy or bend new brake lines from the distro block to the frame. I'm not sure he makes 1/2 ton setups - but worth asking.
Couple of notes that can trip you up...
- make sure that any master cyl you get is for a C10. C20/30 are designed to have the front/rear reservoirs route to different front/back circuits (if I recall)
- master cylinder needs to change - the plunger in the piston (visible from the firewall's perspective) has a different depth hole in it - and the little pushrod between booster and master has to be the correct length. There are two lengths if I recall, one short, one long. Anyway, just make sure they marry up correctly.
You'll have questions as you go along - don't hesitate to ask. I've done #2 and #4, happy with both ways.