Where is this "Data Tag" or "Trim Tag" located on the vehicle? (1965-1966)
Is there a website that can decode this type of tag?

http://www.classic-cars-online.com/tag.jpg

 

The only 3 places the "VIN" would be on a 65-66 will be
1 Drivers Door
2 Cutout on left front fender, the # is stamped on the fender apron.
3 Under the right fender. Again the # is stamped on the fender apron.

The "Trim" codes are only on the tag on the drivers door.

Her is a decoder website:

http://www.mustangdecoder.com/decoder.html

 

The tag you show is screwed to the left front fenderbetween the stamped vin number and the hood hinge.

 

bets thing to do would be to check on drivers door for the tag. there you can find VIN and all trim codes. You can decode them with the decoder mentioned above

 

On the drivers door , and you can buy s book to decode it