Upper Control Arms
I think that is primarily for building tubular arms. It might repair a large ball joint arm too.
Assuming the internal threads shown fit the larger ball joint... Bore the small joint arm to fit its OD and you'll have very little remaining to weld to. What effect will the welding have on those internal threads is my question. Will a ball joint screw into it ? I guess it depends on the welder.
They could make that with a flange on it but the larger material and machining would drive the price up.