Here is an UCA I know came off my ‘74 Duster with disk brake spindles. The spindle is a ‘73 drum brake spindle off my '73 Duster project car. Fits together well, UBJ is the same.
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Funny thing is, I have the drum brake spindle because we converted the ‘73 to disks back when the car was my son’s. And I am almost certain we didn’t change the UCA’s when we did it. I know I had to do a LBJ, but only because I mushroomed the stub. So even the LBJ should be the same disk to drum.
So now you have seen a big ball joint A-Body drum spindle.