I have a 66 coupe 289 c code built in san jose dec 20 66
The two supports that go from the cawl to the top of the shock towers are normal and they are in place. I have seen many 1966 mustangs that have a round bar that goes from the cawl to infront of the shock towers. They bolt to the inner fenders. My car does not have them and I see no evidence that there ever was any.
Can someone tell me why or which cars should have them?

 

First off, welcome to the boards. I cannot help, but I am going to move this to the classics section, there should be a few who can help in there

 

Sounds like you are describing the braces that were on early convertibles.