The torque boxes (or "hog troughs") in an Avanti are perhaps the best known weak spots in the these cars. They are essentially foot wide sheet metal channels, bonded and riveted to the body floor between the frame and the rocker panels the full length between the wheel wells. They were designed to make sure the fiberglass body would not flex on the frame. After exposure to the elements (and road salt in some parts of the country), they start looking more like swiss cheese than sheet metal.
I purchased R4141 a few months ago with the full understanding that at least the left torque box was perforated. There were also some minor "fixits" needed (tach, power windows, trunk release, and a few others). The rest of the car, however, was in good condition. The paint was very nice "driver quality", the interior needed only carpet and repairs to the driver's seat, a bunch of mechanical work had recently been done to the car including all new brakes, new suspension and steering components, new springs, motor mounts, exhaust, tires, radiator, etc. etc.
The price of the car reflected the need for at least one torque box and the "fixits", and I took the chance that I wouldn't run into any other major item needing repair or replacement on the car.