I have cut and welded A7 draglinks before; they are made of quite a thick wall tube and don't appear to be anything fancy in way of material.
If you're going to use the factory "cup and cap" style ball joints you'll want to use 3/4" OD tube which will need to be at least 14SWG wall so that you can machine the 5/8" bore for the inner cup whilst leaving a seating at the rear end.
If you're stuck with metric sizes in France, you could use thick wall 20mm OD tube and skim the outer down to 3/4" at the ends to accept the outer cap and bore the inner ends to 5/8" for the cups.