'67 power steering upgrade

[A1971Blazer]

On this '67 I just bought, I want to add power steering.
After much research, I have seen that the '67 frames did not have the dished area on the frame where the steering gear mounts.

Obviously this one does (picture) which is probably a good thing...
The numbers stamped on top of the frame rail near the gear do not match anything on the VIN number.

Not that I'm overly concerned about it because I have a good clean title and where I live there is no "inspection" of a vehicle this old....
but am I to assume this is likely a later model frame? Or perhaps a very late production '67 that had a '68 style frame.

Are there other identifying attributes that would identify it?