Brat64,
The last time I checked, Burger King in Highland Park still had the tacos on their menu.
I will guess Jack in the Box was likely my very first taco. It was exotic enough for me to drive my teenage friends to Chicago to try. Brave soul I was going to Irving Park and Kedzie, when my grandparents lived very nearby. I just loved those greasy tacos.
I'll take your word the crust is lighter in Jack's version. For my blurry memory, Burger King is just about the only thing that has come close in years. Looking at that picture, it doesn't quite fit the picture of Jack's in my mind's eye. Jack's was more compressed, crispier and had shredded lettuce.
Burger King taco

Now that I think about it a bit more, the brain taco preparation from Don Pedro's on 18th Street might be more Jack-like than Burger King's. Of course, I would never expect brains at Jack's or Burger King.

Regards,