65 Barracuda Speedo Cable

I'm having a new custom panel made to replace the stock one. I tried turning what looks like a grey collar on the back of the gauge but it doesn't budge. I just need to know if its common to need pliers to turn it. As I mentioned not a lot of room there. Seems like should be simple, but with old cars you never know.

Shouldn't be pliers necessary but... old car.

Have you thought of just easing out the whole panel so you're not having to feel around under the dash?