As Jeff pointed out, the standard rifleman and automatic (BAR) rifleman belts had 10 and 6 fixed hodling pouches respectively. The pouches were integral parts of the belts and could not be removed.
There were however no standard "pouch" belts for the other weapons you mention. Specific "attachable" or "slip-on" pouches were issued for the M1 Carbine, the M1A1 submachine gun and the M1911 pistol. These were designed to be attached to the standard, pouch-less pistol belt.
In the case of the M1A1, or Thompson SMG, there were two types of magazine pouches, namely a six-pouch rig for the shorter 20-round box mags and a three-pouch rig for the longer - and heavier - 30-round round mags. Below are links to examples of either type (from "At The Front" and the "Alibaba.com" websites):
There was also a single-pouch variant designed to be carried by means of a shoulder strap, and usually issued to airborne troops during WWII (photo from the "At The Front" store webite):
Ammunition pouches for the M1 Carbine and M1911 pistol used a similar two-pocket design with single flap. In the case of the M1911 pistol, you'd normally see only one such pouch worn on the front of the belt, opposite the field dressing pouch (photo from "5th Ranger Battalion" website):
Note that there were a number of variants of the above, with pointed or rounded flap, and with one or two "snap-stud" fasteners.
The M1 carbine ammo pouch was also a slip-on design intended to be worn on the belt, but the loop on the back was large enough to allow the pouch to be slipped onto the butt of the carbine, which was common practice in the field. In was slightly "stubbier" in appearance than the M1911 pistol mag pouch (photo from "At The Front" website):
Of course, by the 50's (Korea), the M2 Carbine (M1 with full-auto mode and 30-round "banana" mag) was replacing the M1 in frontline unit, and thus a new, longer single-pouch mag was issued to accomdate four of the larger mags (photo from the "J. Murray Inc." website):
Hope this helps.
Hervé "Charby" Charbonneau