1985 Corolla Ball Joints

I have a 1985 Toyota corolla SR-5, 1.8L engine with 120k miles.

My question is: Can I replace only the ball joints and not the whole control arm/ball joint assembly or is this some kind of one piece unit?

The ball joints need to be replaced. The dealership and manuals state that the control arm and ball joint must be replaced together but, no explanation beyond that.

I have been able to purchase the ball joints ($60 for the pair) but, before I start I don't want to get it all torn down only to find out that I do need the $1500 control arms.

I can't tell from looking at them on my car and I can't seem to find any explaination on whether it is possible to only replace the ball joints independent of the control arms.

Thanks,
-Lou