What's the best way to fix this? My son tried to weld it but being, by the looks of it cast metal, he didn't make a good job of it. It's the hook that sits under the rear passenger side of the floorpan.

don't think you can fix that

It should be cast steel and not cast iron so should be weldable with the right amperage welder plus making the weld area completely clean by grinding and degreasing.

I remember welding my new floorpan to that hook to pass the MOT in UK.

And preheat the steel if you can do so without setting it alight.. Will help a lot.

looks like someone has already had a go at welding it

May be better to make a bracket to take its place its only to stop the end of the torsions tube from wandering around

Cast steel and you will need a rod like a low hydrogen or a weld all, quite expensive for the rods.

Easy fix with cast rods and pre heat the area done mine ten years ago and has not failed but if no confident best get a welding shop to do the job

It puzzles me why they break at that spot. Perhaps use of a scissor jack on that point?