disk brakes not power?!?

[FrankHoy]

I got a suprise today, working on my 71. I noticed that it has disk brakes on the front but does not have a power booster. I had purchased the truck at night, so never looked very close at the brakes before. They have always worked but definitely NOT power. I had just assumed it was all drum due to not having a booster. I believed this to be an all original unmolested truck, excluding a different bad paint job. I have a couple questions, hopefully some of the brake experts can help with.

First off, is this common or did this even come from the factory like this? My option sheet on the glovebox doesn't mention anything on for brake option?

If this did come from the factory like this, can I just add a power booster? I do have a couple extra, complete with master cylinder. Would anything else need to be changed?

Any insight greatly appreciated!