Scamp suspension
The top frame does very little for the rigidity of the car when its up, and none when its down. I cut up a convertible years ago and I found no hidden bracing. What it did have was the torque boxes underneath, like on 340 cars. If the doors shut good, and the panel gaps look good, its probably ok. Put in frame connectors pronto, ones that weld to the floor. Best thing I did.