Bracing shock towers?

BO70, YES! Spot welds are fine for most applications and duty, however, for racing and hi powered engines, welding the whole thing up can't hurt and so long as it is done right, (Good burn through) it'll be stronger.

I did my floor pans this way (Perimeter weld on the patch pans.) and tack welded them to the frame via holes drilled into the pan like the factory, just more often.