I'm a little spooky about welding on suspension parts. Chances are it will be OK, but a few decades of building dirt track race cars has taught me that "Where there's welds, there's gonna be cracks!" That's particularly true of welding cast steel (or cast iron) spring mounts to a mild steel frame. I'd recommend inspecting those welds on a regular basis with a strong light, looking for the beginnings of stress cracks. There was a good reason the factory chose to rivet them instead of welding.
Jerry
