I had never believed that a rivet would allow movement, and that it was a "safety" device vs. welded.
Henry Kaiser believed the same thing; google "Liberty ship" to see what happens when you weld a chassis that should be riveted.
IMHO the area that is most likely to cause a problem is where the steering box mounts to the frame. The leverage of power assist, bigger front tires and heavier engine make for a lot of stress compared to the original; if the joint isn't strong enough it will flex every time you dry-cut the wheels.
