The brakes should act the same regardless of which master cylinder in attached to the booster. If the booster is malfunctioning, the engine will miss when you apply the brakes, plus possibly the hissing sound when the booster is operating.
FIRST, though, make sure the brakes are adjusted properly and the brakes start to apply near the top of the brake pedal's travel. NOT 1/2 way down as most GM's do. THEN, remove the drums and spray them down, the linings and the drum, with brake cleaner. This will remove the accumulated brake dust. Dispose of the collected dust properly, as it might have some asbestos in it. Reassemble to specs. THEN see how much positive difference that can make in how your brakes act. With the drums off, you might procure a "brake drum caliper" that will also match the brake lining adjustment to that drum diameter.
To me, do these things FIRST before you start seeking to adjust the booster's push rod (from the brake pedal) or the master cyl pushrod (between the booster and the master cyl). These things typically do NOT get out of adjustment with use, so once set at the factory, no need to mess with them as the car's age progresses.
Back when "the air was clean and sex was dirty", our service station guy recommended that we get the brakes "blown out" with ah air hose. Getting the accumulated brake dust out of the drums. It made a significant difference! But it dusted everything in the dealership's service department. So, that's why I mentioned getting the linings/drums cleaned up, in the more environemetally-friendly manner that we have to use now.
Just some thoughts,
CBODY67