Hi. The front tires of my Plymouth GTX 1970 are leaning out at the top when I make turns. The ball joints are good, the control arm bushings are fine. Any suggestions where to look? Thanks in advance.

That’s Castor, and it’s a good thing….as long as it’s positive castor. The drivers side should lean out at the top during a left turn, the passenger side should lean out during a right turn.

What I'm picturing would be called camber change.
Inside tire (LF on left turn, RF on right turn) leaning in at its top when cornering - look at pretty much any photo of an older car cornering.

Caster is the inclination of the spindle fore/aft, best viewed from the side.
Camber is the inclination of the top vs bottom of the wheel/tire, best viewed from the front.

Caster is what makes the top of the tire angle when turning, in addition to providing a more stable track. When you are measuring caster you are actually measuring the camber change of the tire at two different angles, usually + and - 20 degrees then caster is inferred from that.

Camber is mostly the same thing (angle of the tire in or out) straight ahead, though there are inter relationships between the two.

Camber change would be the tire (or body) moving up and down. You want the top of the tire to lean in a bit in relation to the frame as the body weight shifts in that tire's direction so that the tire is squarely planted in relationship to the ground.

^^^ Yup. They do interact.
I was separating the 2 into the simplest visualization.