Ideas? On a drill jig for converting Magnum heads to LA intake

Not sure about that Pishta. I think there is no "straight shot" into the angled LA holes. I don't think you can just mark them, either, I believe the magnum holes "interact." That is I don't believer there's a clean surface for a transfer punch, etc.
your right, the holes do share some real estate. I think if you could sink a carbide burr or an end mill into the guide, you could make a pocket that a smaller drill could find and then create a pilot hole. Not something I would try with a cheap bit. If you got the know how, go for it, sounds like you got a good plan.