Saiga AK: 13 mags
AR-15 SP1: 12-30 round, and 3-20 round Mags
VZ58: 10 mags
(2) M1Carbines: 7-30 rounders, and about 25 or 30 -15 rounders
Seriously, years ago when I was doing gun shows a lot, there were some original "issue" packs of 5 fifteen round GI mags sealed in a package. I have read somewhere that typically they had one to three belt pouches, maybe a stock pouch, and one in the weapon. My dad said on Iwo, he had one in the carbine, a stock pouch and a belt pouch. He said if the Japs got to him and 75 rounds wasn't enough, he was in deep sh@t anyway!