What is the name of the "T shaped" screw in place metal bars that are used to stiffened the body of a targa top vette (93) when the targa top is removed ? I have seen in the past.

Why do you think you need a bar to replace the Targa tops when removed? Chevrolet made the Corvette cross bar strong enough to hold the frame rigid enough to hold the car together and not compromise the ride or handling when the tops are off. In 1984 through 1986 no convertibles were made until Chevy was able to find a way to strengthen the body to federal safety standards to make a convertible that did not have the cross bar to hold the frame rigid. In 1987 they came out with the first convertibles in the C-4 Corvettes. I have seen them advertised in the 80s, but never knew anyone that used them. If your racing your car, most rules will not allow the tops to be removed anyway. If your concerned, get glass tops that will give the hold your looking for and also the view as if the tops are off.