I see some slight differences in all three but I'm blind anyway, so who's to say!
The vins do appear to be hand stamped but are a lot straighter then the Willow Run stamps I've seen, they're all over the place!
Here's another Norwood block I've had under a bench for 30 years and I know hasn't been messed with. Thought for sure December 14, 1965 was going to be a Monday as the stamper left off the last digit of the vin but turns out it was a Tuesday.