We appreciate classic Mustangs just as much as the next person, but they did come with their fair share of annoying and sometimes dangerous design flaws, such as cowl vents that leak, seatbacks that easily brake, dangerous braking system defects, defroster air doors that fall apart over time, parking brake mechanisms that too be honest never worked well, door latches that froze, and shock towers that cracked. Cracked shock towers are not only hard on front-end alignment, but also dangerous, a crack can turn into a highly dangerous shock tower problem and complete steering system failure.
To understand why Mustang shock towers crack, you have to know a little about Mustang suspension systems themselves and how they were designed. The classic 1965-73 Mustangs have a coilover upper control arm front suspension system. By using this design Ford was able to save some money which brought the overall cost of the car down but, it was not a good design in terms of strength, reliability, and overall handling. The Mustang also had another serious design flaw, the upper control arm binding and having to handle unwanted slack. If the upper control arms bind, the shock towers flex with suspension articulation, this causes metal fatigue and can lead to cracking.
The 1967-70 Mustangs have the same basic shock tower, they are different in how they connect with the rest of the body. This means a different center apron and different part numbers. Dynacorn has created a shock tower different from original equipment; is its heavier-than-original gauge steel construction, which makes it even stronger than the factory factory specs.
The shock tower cracking seems to me mainly focused on the 1967-70s models so anyone with this car or in the process of doing a Mustang restoration might want to inspect your shock towers very carefully.