By the way that swingarm is distorted where the shock mount goes I would beef it up in one if two ways.
Fabricate a new cross peice out of 3mm wall thickness RHS and make up some new mounts.
Or cut off the shock mounts and reinforce the existing cross peice with some angle iron welded over the original. Weld on some new mounts and it will be all good.
If you just weld the cracks that cross peice will continue to distort and the cracks will reappear around the new welds very quickly.