You don't say what size truck you have or year. I assume it's a 48 by your "name"? Brake booster's are called Hydro-vac's on these. They can be on opposite frame side or on same side outside frame as on my GMC COE's. Yes, there is another brake cylinder on it, and Yes, bleeders, two on it. And they have to be bled in order to do right. Use ONLY a GOOD fitting flare wrench or six-pt socket or wrench on them. Use penatrant oil sparingly on them, let set a day or two and start to loosen, if it moves, STOP, and re-tighten some, let set awhile, go back and move some more. Work them back and forth till they come all the way out. Clean them up good or replace, make sure holes go all the way thru with wire poked in them. Replace and bleed. Most times these will break off, and the cylinder is rusted up and pitted just like the Master Cyl is/was. The chamber has a vac line to it and a leather Piston seal that dries up and needs replacement. It's a very complicated unit, and parts are hard to get. Most brake shops just send whole unit out to rebuild, around $250 I'm hearing. My 54 has one, I got it to bleed, don't think it works at all and have been driving with "regular" brakes for 5yrs. now. An old 59 F-truck I once had with same system would stop on a dime like power brakes and make vac sound when I let off the pedal. Mine does none of this. They do work, yet with a load are NOT very good. I plan on working on or sending it out this year to make them right. Biggest problem on bleeding is the two rear wheel cylinders are hard to bleed because of position they are in in the drums. Have to do them in certain order too. I once had a 76 F-truck with about same unit on it, so pretty sure same systems were used long time. I was thinking of maybe using a later model unit on some of my old trucks as I rebuild. Lots of later models went to a Hydra-vac system that runs off the power-steering pump and uses no vacumm and are on firewall with MC. These are used because of Diesel's not having Vacumm to run brakes on. We are now putting those on all 3/4-ton HD's and one-tons in truck plant I work at (Chevy's). You will find that sitting around will cause you to replace most of the brake systems on these old trucks and be very expensive and hard to find parts to do it. Good Luck!
