Odd Frame Repair?

[kiwi nz]

The way I understand it these frames are designed to flex in order to take the twisting force of the transverse spring.
There is a woven pad between the spring and crossmember that helps take the load off the crossmember.
When this is left out the repeated loading becomes enough to fatigue and crack the crossmember.
I would repair the crossmember with new metal and replace the woven pad.
The crossmembers are hot riveted in place, they are held extremely tight, any replacement process will need to produce the same rigidity or the joint will eventually come loose.

By the way that is a beautiful car, Autumn brown is one of the nicest colours of that year model.

Geoff