The 123GT got the high compression B18B engine in '67. That was not an option on the 122. It was only available in the 1800. In 1968 it was available as an option in the 122. I'm not sure this is the original engine but I haven't checked too deeply yet...

So by the grills, I'm guessing it's a 68 1/2

I've got a straight set of grills for a 66-67, they are as perfect as I've ever seen.

As for the rust, it's not any worse than the red car, just no bondo. For me, I'd vote against a car cover. They don't stay on and can be a problem keeping moisture in contact with the paint. The Princess had small portable car ports with tarps for $100 a little while ago.

Which grille would you be basing that on? The left one or the right one?

It's a '67, based on the serial number. I believe the guy said that he had the proper grilles in a box somewhere, but I could be mistaken.

The 67 is on the right and the 68 is on the left. I've got a straight set of the 67's.