Here's a pic of the setup on the laser:
It's my miter saw, but it works and I have it on hand!
The neck is just sitting there for the pic, but I held it tight in the pocket, lined up the neck, then removed the neck without moving the body.
I used a pencil to trace the centerline down the body:
This is the lowest tech way I could think of to mark the four new hole positions:
A 1.5" x 2" square piece of paper with a centerline drawn to hold up to the centerline in the pocket.
Mark the corners: