340 TA with x heads ? or not

I am looking at purchasing a 340 engine that supposedly has the "x" heads.
The block # is 2780930-340
Head # 2531894
vin on the motor LS23P9E123831.
I looked thru a few threads but it didnt answer my question.....are the heads the "x" heads ????
I know the motor is out of a 69 dart GTS, 340 w 275 horse according to the vin# decode.