It would be my understanding that it should have a serial number of the car it was installed into on it as well. I don't see evidence of that having been ground off in the pictures.
It does obviously have a few new parts on it as well. Probably internally too.
The tag looks good to me and few will be able to tell for sure unless you have seen lots of the originals so I don't think there is harm done there. The casting dates need to be appropriate though to a 67 GT500 production date.
Nice original CJ versions, like the RUG-AE's, have asking prices in the 3500 to 4000 vicinity that probably aren't this clean. Then there is the shifter, the rods and maybe the gear reduction adapter that can be involved to consider as well. A rather expensive proposition as a whole.
This one is probably better suited to a "tribute" car rather then an original but seems to be priced appropriately for that application.
I'll need to read the description again but I don't remember at this writing of it saying original? Just rebuilt.
So many of the original cars lost their original as built parts in their first few years of use. Few cared at all including the Ford Service Department of installing original assembly line replacements as if that was even possible at the time.
On "restoring" a 67 GT500 there IS going to be some sort of compromise along the way on certain items. The number that are going to be original as built cars is going to be literally just a handful and even those who think that they have one are going to be embarrassed at some point to find they have replacement parts on the car.