Replacing front shock absorbers...how to get that insert cap off?

[Franks89-911]

I have an 89 911 with Boge original shocks.

I am replacing the front shock absorbers. I've gotten the top nut off in the frunk just fine, and pushed the shock down and outside the fender.

But, I am unable to remove the caps on the top (see pic, below the rubber part) to remove the shock itself and replace.

From what I've read, channel lock pliers should get it, but no luck so far for me even with penetrating oil.

Advice?

Thanks.

[JRSIII]

I was able to get mine off with a couple of pipe wrenches. One on the gland nut and one one the strut housing for backup to prevent putting a bunch of torque on the ball joint.