Any of the good taco trucks in S. OKC and mid OKC will serve lingua (cow tongue) tacos. Fung's Kitchen has a B menu that's written in English that has their authentic chinese menu, which is full of awesome authentic cantonese food that beats the crap out of the Americanized crap that comes frozen and served in most Chinese restaurants and buffets. They range from roast duck, crispy pork, beef and flat noodles in black bean sauce to "weird" things like their fried frog legs (really good) and jellyfish, ect. Tokyo Sushi in north OKC has some authentic sushi from your traditional nigiri to sea urchin.
Excellent suggestion, I've been wanting to try some traditional tongue taco's and such. I've heard the Menudo at Casa Perico is supposed to be very good (only served weekends).