1968 lower ball joints question

[JDS68Stang]

Replaced most of the front end so far and still steers hard, have to pull wheel back w/ equal pressure after a turn also. Replaced PS control valve with a (Flaming River) and new slave cylinder, valve set to correct lenght (4 7/8") and adjuster behind dust cap was set @ 100 in. lbs. then backed off 1/4 turn. (I've heard the Flaming River valves are built to tight ?) Lines are hooked correctly.

I was told the lower ball joints could be the cause, they seem OK when I try and rock the wheel once up on a jack but was told the spring is putting to much tension on them to test that way, is that true? if so what's the best way to test them? We just put in new upper ball joints.
They are original w/ 3 rivets. (got a 6 banger).

Also I'm pretty sure the steering box it ready for a rebuild, it's real touchy in a straight line, I've read the center gear has a tighter tolerance and will act up when worn down. We've tried adjusting that as well, no luck.

Any thoughts on how to properly check the lower ball joints or tips to replace?
(planing on a cross cut then chisel on the rivets for their removal)

 

[Grabber70Mach]

I was always under the impression that you had to replace the complete arm when replacing the lower ball joints. I know that some manufacturers make a screw-in ball joint that you have to weld a threaded piece into the arm then screw in the ball joint assembly. This enables future replacement without having to replace the arm.

 

[JDS68Stang]

I'll have to look further into that, I'm a certified welder so weldings not a problem. Last I checked it looked as though they'd pop out fast w/ the right tools.
This isn't something I'm going to get into till about two weeks from now, to much going on remodeling the house and all.

It's just a b*tch when you spend good money repairing something and then you have to wonder did they send me a defective part (PS control valve) and not have the option to rule that out since it's new, as a source of the problem.

I'm wondering if I have to take the load off from the spring to check out these lower ball joints?