Brake Booster Guidance Needed

[EdSevered]

Hello all,
I am the third owner of a 71 Cheyenne 1/2T (avatar) with factory manual disc/drum brakes. Not knowing the truck's history, there are certain things that I feel like I should get new and completely replace, such as brakes.

I am in the process of collecting parts to redo the disc brakes and I'd like to install a brake booster with new master cylinder and proportioning valve. I have already purchased rotors and loaded calipers from R1 Concepts, and the Timken bearing kits. Next I am looking at getting hoses and the booster. Will redo the drums on the rear shortly.

As Brake boosters come in a variety of sizes: 7", 9", 11", etc., can I assume that the smaller the size the less "boost" assistance will be provided by the unit? If I plan on keeping a mostly stock vehicle, maybe a little lowering later, what is the smallest size I should I consider? Are there any other things that need to be considered?

Any recommendations on brand and/or place to purchase would also be appreciated.

TIA!
-Ed