I have a 68 falcon that I stuffed a 429 into- fit wasn't a problem. Have about 1/8" of clearance on either side between the manifolds. It is solid mounted, and the car runs pretty smooth on the drive to work every day. However, getting a fan to fit on it was quite a challenge- had to modify pulleys so that the fan would bolt on without a spacer. Considering I was working outside on the dirt and had to put up with hurricanes for three weekends in a row, I'd say the car isn't too bad. (especially for a first-timer like me!) I don't really know how the shock towers on the mustang differ from a falcon's- to a novice like me they look pretty much the same. I have heard that ford did modify them to fit those monster 429 boss motors...