Ed - Well, here is more more interesting info. I found this picture in the '68 Chassis manual. Unfortunately, the picture is for a 6 cylinder engine but the interesting thing to note is that it clearly shows the wire type clamp.
Mike - What is the build date on your cars?
It's still a mystery to me why some cars have stamped clamps and others have wire clamps, particularly in light of what Ed reported in an earlier post. It also doesn't look like there is a rhyme or reason as to which size engine got which clamp since the Chassis manual shows a wire clamp on a 6 cylinder engine.