This truck appears to be a civilian truck purchased by the Army. There were thousands of these purchased by all the services. I got my Navy heavy truck license on a brand spanking new '47 five ton GMC flatbed.

These trucks were usually no different than civilian trucks: however, it appears that yours was ordered with the same 302 engine setup that was used in a tracked amphibian and the M135/M211 series of 2 1/2 ton 6x6s being built at the same time. this was probably done for commonalty of parts. The above vehicles also had Hydramatic Transmissions but I never saw any civilian types with AT. The amphib had two 302s and ATs.

I can't find a 424V listed but I do know that it is a 400 Series which is the 2 1/2 ton. The 2 means a 302 and 4 has to do with the wheelbase. I don't know what the V means. Most V8 trucks then had model designations something like 450-8V if they had the 316 or 347 V8s. I have a '53 633. It is a 5 ton with a 503 straight six, it looks like a bull.

'31 Chevy 1 1/2 ton,
'42 GMC 2 1/2 ton 6x4,
'52 GMC 2 1/2 ton 6x6,
'53 GMC 5 ton