I know the '73-up UCAs are the ones hunted for by those wanting to
upgrade to disk brakes, but I don't know how to tell the difference in
them vs. the earlier ones. Doesn't it have something to do with the size
of the ball joints - what do I look for? Anything for me to measure so
I will know?

Jerry

_________________
There's a difference between ignorance and stupidity.
Ignorance is not knowing any better.
Stupidity is knowing, yet doing it anyway.

The difference is in the size of the ball joint in the upper control arm. The 73 +> A-body disk brake cars used the same ball joint as the 68-70 B-body cars. The tool catalogs say the size for the 66-72 A-body is 1.809 and the 73 +> disk brake is 1.915.

_________________
You can't fix stupid. - Ron White

Thanks, man. I have two sets of UCAs that came in a pile of
parts I bought. Comparing the two, I see what you described.
The UCAs look the same; however, there is a significant difference
in the ball joints.

I appreciate the info,
Jerry

_________________
There's a difference between ignorance and stupidity.
Ignorance is not knowing any better.
Stupidity is knowing, yet doing it anyway.