I don't remember any cast IRON manual steering boxes, just the aluminum types that have been on cars since at least 1962.
If there's IRON units out there, then that's new news to me.

I do know that when I removed my cars original IRON power steering box (49 Lbs), and replaced it with a manual aluminum unit (14 Lbs) it removed (35 Lbs) from the front of the car.
I can't remember if that weight savings measure was indeed correct because I didn't include the assorted hoses, fluid, belt, the pump, pump bracket and pulley itself.