Power steering gear nightmare

[Tully]

I put a different steering sector on my 72 K20, when I pulled up to the garage the power steering worked, but the sector leaked. The new one (junk yard) seems to work fine to the right with one slightly stiffer spot, but to the left the pump whines all the way to the stop. I have the front end up off the ground. I bled the system buy going stop to stop, ( probably 50 times by now), always keeping fluid in pump, I also cracked the return line a few times. I let the truck set for hours then tried it again, then over night and the same. I think I got another bad sector, what do you guys think? This is the third one from this yard and I didn't get one back in 90 days so I have $125 in this deal. The yard is over an hour away and I had to wait 4 weeks for the last one. If I ask for my money back I will only get $50. The guy is as sick of me is I am of him so I want to be sure it's the sector before I call back, so what do you guys think the problem is? ( I know now I should have went with a rebuilt but I am buried in this deal now)