You betcha.
But, it doesn't clear up anything for 67.
My correct metal tag -- I assume it's correct due to the correct-for-my-build date, axle ratio, and 'other markings' (plus all the correct attributes of my housing and brakes) -- has a Sterling plant code that is at odds with the 68 chart.
In the Perkins write-up the axle tube's hand written plant code, the paper tape and the tag all agree.
I'm not going out on a limb and saying 67 GT350 axle assemblies would have a 70-style hand written plant code on the tube as I find no evidence of that on mine (yet), but one would think (uh-oh, here we go) that at minimum the tag's Sterling plant code and the paper tape would agree.