Cast pistons would have worked fine in the stock cobra application. If you look at other OEM forced induction vehicles you'll find various types of cast pistons used. I'd venture to say the only reason ford put forged pistons in the cobra was because they new what the public was going to do….up the boost! And, while upping the boost certainly would void the warranty, the bad press that came along with engine failures was probably not worth it.
Ding Ding, we have a winner
Shakerhood - You have to recall, that the 96+ blocks all started getting stronger, to the point where they would now outlast the hyper pistons typically.
We are talking about '93-'95, are we not? The block (in good conditions) will let go, before the hyper pistons.