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.
I think saying Magnum heads are "better" than LA heads is a stretch. IMO, they're "different" and that's about all.