Cam degreeing on a magnum motor

You would ideally to get to the body of that hydraulic roller lifter and not load on the plunger.

But however, if you press on the dial indicator spring and it is a lot softer than the plunger spring in the hydraulic lifter, then you are fine to go direct to the plunger. The problems come when you have the heads on, and the valvetrain assembled.... in that case, the valve springs are going to be a lot stronger than the plunger springs, and that is when the problems come up.

If you can do this with the heads off, or the rockers off, and just the pushrod and dial indicator, then you should be fine. Just be sure that the lifter moves back down after the lifter goes 'over the nose' of the cam, as the light spring in the dial indicator may well not push down hard enough to make it follow the cam 100% on the closing side.

Hope that makes sense!

And, dealer service on stock engines is not what this is about!