Replaced Power Steering Pump but still have same problem. Your thoughts?

[Old Yeller 1970]

I replaced my few-years-old rebuilt power steering pump with another rebuild because it quit working. It was making that familiar growling noise and was hard to steer. However, after installing the new one I still have the same issue. My dad thinks it may be a bad rebuild. Since it's such a pain to replace, I want to make sure I'm not overlooking something else and I'm wondering if there could be something wrong in the gear box that could cause the same issue. Has anyone else had this happen?

FWIW, After turning the wheel, I've noticed that the power steering fluid is foamy when I look down into the reservoir.