Right, the ID plate will say 304, 345, 392, whatever the size is. It is kind of behind and in the area of the fuel pump, and isn't very big- haven't really checked for mine, I pretty much know what I have. The IC 392 has the water pipes from the water pump going to the block instead of to the heads like all the other IH's did. From what I have heard, you can't put 345 heads on an IC 392, but you can on the earlier non-IC models. There again, if it is an older model, it will look 'identical' to a 345, so you are back to hunting for the ID stamp to make sure.