Tank is a Pershing. Just compared pix of the T34/85 and the M26. The M26 has an external mantlet like that shown while the T34/85 has a flush mantlet that is kind of surrounded externally by the turret. Also, the rib you see on the barrel support is dead on for the M26. The T34/85 has no rib on the barrel support. Close up of the pistol looks like the M1911A1, though the picture is grainy and the arched mainspring housing is obscured. The Jarheads look to have the "Brown Side Out" on their helmet covers which would go with the fall time frame of the operation. The man with the Garand looks to be using ammo made prior to '43 since the bandoleers appear to be tan and not OD. All of this is MHO and could be subject to correction. Cheers, Bruce.
P.S. The Captain might have been around Saigon enough to have purchased some non regulation boots?