overheat only over 3000 rpm

Water pump impeller distance to the back of the timing cover can be off and cause flow issues and cavitation. Cant assume any parts now a days are good or assembled right. A pump with a round disc on the back of the impeller eliminates the problem.

Also you mention fans pushing in the right direction, and that they are mounted on the back side of the radiator. Mounted like that they should be pulling air not pushing it.