I actually impressed the hell out of myself. I was in the garage making a jig to layout holes for adding a windows key to F122 and unsaver plates. Well I took some measurements, drilled some holes, ran some maths, more measurements, drilled another hole. And my hole for marking the actual additional hole on the IBM plate, came out within .002" of dead center between the other holes in the jig. The other holes fit over the two barrels on either side of the new switch. And this is all I used for tools for the entire project.
Now I just need to figure a jig for holding he plate so I drill the holes square.