signet -65 frame

The windshield frames are different. If you need a windshield just find one for a hardtop. The convertible cars had "torque boxes" welded into the frame to make up for the loss of stiffness the roof provides.
The torque boxes are available and can be found on the web. I would also recommend "frame connectors" for some more added stiffness.

I'm guessing that you are not making a convertible, but just a topless runabout. I hope this helps.

ATB

BC