In my eyes, the 69/70 Shelby is the best looking pre 71/73 Mustang available. I imagine the reason why I think so is because they look like the 71/73's.
As for other cars similarities (what is that saying about copying being the purest form of flattery?) - the reasong the 71/73 Mach 1's excell is that they are a complete package. No doubt the pretty face is what first grabs your attention but the 71/73 Mach 1 is not just a pretty face, it also comes with a heart of gold and a soul of worth, willing and eager to take on lifes challenges and stay right with you. And to beat all at the end of the journey the inheirent beauty that drew you at the first is still there.