67 ? K20

[Nickclimbs]

I recently bought a truck that has a 67 K20 cab but I don't know what the rest of it is? It was upgraded to a 3/4 ton dump body with heavy duty springs and a 4 speed transmission at some point but I do not know when so ordering parts seems a bit tricky not knowing what is really under the hood? The vin# on the door post says it is an 8 cldr but it has a straight six in it. 292? the number on the block is to the rear of the engine mount GMC 473483 Any help would be appreciated. thanks, Nick