Bleeding the Power Steering

[Pappyx3!]

I have air in the PS can't seem to get it bled. I have raised the front wheels and turned the wheels from side to side (EO) at least 15-20 times on 2 occasions. I'm getting the grinding sound like the fluid is low (intermittent) and once I shut the truck off it will push the PS fluid out of the reservoir. Tried everything I know, any suggestions? Thinking I may need to replace the PS pump...

It's a 1962 C-10 383 Stroker, think it was fitted with the pump and gear from a 1968-1972.

Thanks for your thoughts,