K10= 1/2 ton 4x4 Chevy truck
K20= 3/4 ton 4x4 Chevy truck
K25 and K2500= 3/4 ton GMC 4x4 truck. I have heard 25 and 2500 used to refer to the same truck, but the 2500 was probably a higher option GMC truck, like a Sierra Grande. There may be a GMC K15, which would be a 1/2 ton 4x4, but I'm not...