My opinion would be that a May built car is definitely "late" in the model year, even if not so in the calendar year.
That would have been within three months of the end of 67 production.
Though not definitive, I would not over think this (well, then again maybe I would, as I have a tendency to do so on my own stuff) and just look for a correctly dated 210 carb. Easier for me to shoot from the hip and make the call on someone else's car!
I cannot imagine any scenario where anyone could challenge that as being correct.
Here is one dated March 7:
https://www.ebay.com/itm/256199789589
Not knowing who "remanufactured" it, I would look for a core and send it to Eric Jackson. He da man. Have used him multiple times with nothing less than spectacular results. I know he got sideways with some Corvette guys, but he has never been anything but good to me.
If you are not wanting one fully restored, you can rebuild yourself. They are not difficult to work on. Just make sure you get all the numbers for jets and other parts, to make sure someone hasn't been in it before trying to "improve" it. On my 68 El Camino, I found that recurving the distributor, running about 10 degrees initial with 36 total and plugging the vac advance to manifold vac allowed me to go down two sizes on primary jets. Got fantastic gas mileage on the highway for what it was. OD trans helped I am certain. Your results may vary.
If for some reason you don't want to use Eric, there is another fellow now sponsoring (I think) on this site that has had great reviews for carb resto.
Good luck.