has anyone put a magnum cylinder head on a la engine? if so is it better or worst? and what does it take?

Far far better. LA or mag head gaskets (get the thickness you want & get quench if you can). OE mag rocker setup (which might be NS1 by now) or for a perf app go with the chebby studs stud rockers & poly locks. oil thru pushrods needed (most lifters are oil thru but check even if the hole in the top cup has the hole & most all do). intake with mag bolt pattern or can carefully redrill the mag heads to for the LA intake & reportedly you can redrill the LA intake to the vertical mag pattern then some angled spacers on the bolts (ain't done the last one yet). Google or youtube it & you'll pull up lots of info. You're reducing CC's so keep that in mind along with the rest of the build in your head

Here ya go - Magnum Heads on Older LA Blocks

Much easier to put Mag heads on LA blocks than it is to put an LA head on a magnum block, and most magnum designs flow better than their LA counterparts.

there are a few though like some of the "P" race heads that are LA style that have lots of flow