I'm still trying to track down a Magnum non/AC alternator bracket. Then I'm going to pull my engine and align the Magnum accessory brackets off the one hole one the bottom of each head and use transfer punches to mark the other holes needed. Then i'm going to drill and tap the heads for the magnum holes. I'm pretty sure this is the most straightforward way to do it on a somewhat budget. I'd ask IMM if they are able to drill and tap the Magnum holes on those heads before the engine is assembled, that's the best way to do it.
