[Msquared]

The stock parts are plenty strong enough. They only have to react loads in tension and compression. Their stiffness in bending doesn't matter at all, and you want them to be flimsy in torsion since they use axial bearings but need degrees of freedom in other axes as well. If they were uber-stiff in torsion they would add undesirable bind.

There are good reasons for some people to switch to aftermarket suspension links, but strength isn't one of them. I mean, nobody really thinks GM would release a car with suspension links that are too weak to hold up to severe use, right? Mainly you'd do it to remove the impreciseness of the factory rubber axial bushings and replace them with spherical bearings, and to get a stronger type of adjustment than the factory eccentrics and a wider range of adjustment.