The magnum balancer is about 1/4" or so thinner than the LA. The hub itself is still in the same plane as the LA however so the pulleys would all line up if you swapped the timing cover/ water pump/serpentine drive and all. Magnum heads have 10 bolt valve covers but the LA covers will bolt on them. I have LA covers on my magnum heads as well as all the front drive system on my LA block. The magnum flywheel would have 8 notches on the back side for the crank sensor to read, the LA flywheel does not. Magnum heads also use the 5/8 hex spark plugs where the LA uses 13/16 hex. Also the bolt bosses at the ends of the heads are not the same so you may need to fabricate a little if you want to run all the LA accessories with the magnum heads. Putting the magnum accessory drive system on an LA headed engine is not feasable.