Drilling Magnum heads for LA intake pattern

I've been following this idea. I'm going to airbrush paint into the la pattern manifold holes while it's sitting on my magnum. Then pull the manifold off and the paint will show where the holes should be drilled. Make up a jig to to hold it in place. Punch the center of the holes and drill them out, then tap the holes. If I'm off a little I'll hog out the manifold bolt holes a little.