FWIW, I wouldn't consider buying that trailer. In fact, I wouldn't accept it as a gift. You could pour several thousand dollars into the restoration of a trailer with a compromised frame structure. That axle mount girder is very substantial, as was the force required to distort it. As stated above, you will find better trailers for restoration. IMHO.
Nick Crowhurst, Excella 25 1988, Dodge Ram 2500 Cummins Diesel. England in summer, USA in winter.
"The price of freedom is eternal maintenance."