I pulled out the shock/spring in the rear of my '73, and after compressing the spring, I can't get the top nut off to remove the spring perch. When I twist it while securing the shock, the inner actuator rod just spins with the top nut. I'm afraid to clamp down on the actuator rod while loosening the nut. More PB Blaster?

There should be flat sides to hold with a wrench; that is, two wrenches are required. Hold the rod with one, turn the nut with the other.

I was concerned that by grabbing the rod with pliers or a clamp and loosening the nut I would damage the shock rod. Thanks

The upper most portion of the rod...way at the top..has a place for a 10mm wrench...almost funny imho.
Use vice grips, but be careful not to damage the threaded portion, just grab above that...its the top 1/2 inch or so...

Rich

Thanks, will try that tonight.