Yes, but if your going to do that, you might as well start hitting every seam. Cars are put together with spot welders, not seam welds, so anything you do will be an improvement. I've always used this analogy, would you rather have a shirt that is sewn together or buttoned together?
FWIW, I read an analysis of a builder who welded up all the seams on a 1st gen Mustang. Testing before and after the modification showed a torsional stability improvement of 65% after welding.
Also worth noting is that SCCA prohibits seam welding in street classes, so it obviously is an advantage.