Its hard to say. My Ford book lists the 390 2v as a single exhaust. But from what I remember, please correct me, but the 390 X was not originaly intended for the Mustang. Check to see if you have hangers that look like an inverted Y. These attach to the muflers in front of the axel and bolt in at the upper nethers of the axel well. If you have hangers that have a doughnut and bolt in near the lower rear seat then this is for a transverse (single mufler behind the axel) dual.