Scream'n 318 ?

Other than heads, is there anything that makes a Magnum block more special than a roller cam LA block? I heard theres some magnum 318 blocks that have really thick walls and can take one helluva overbore. Casting #s on those? Casting dates? What to look for? Lots of magnums in my junkyard.
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Correct me if I'm wrong but I believe the Magnum block has a shorter deck height than the LA motor.