67 Barracuda Rotissarie

People will tell you those door jamb braces are only needed on ragtops. I would put some diaginal bracing in the doorways even if I had to make them myself from pipe. Then I would weld in frame ties.
My theory... After 40 years sitting on the wheels the metal has surely fatigued and the car has sagged a little. First time you turn one upside down it's gonna go back atleast some small percentage of the amount it sagged. Lets compare it to a tin can. So much strength is lost in the first bends. Flipping the car over and over would be just like breaking a tin can.