Magnum Block Education

This website is a very good read

http://www.magnumswap.com/using-la-parts-on-a-magnum/

I don't know what you mean "early and late" all magnums oil the same. You may be confusing LA with Magnum

There's an adapter made for the magnum cam to restore the fuel pump, and you can use the earlier LA timing cover

You cannot put LA heads on a Magnum, but you can (with the right parts) put mag heads on an LA

LA heads are shaft rockers, oiled up through the block and through the shafts

Mag heads are oiled through the lifters/ pushrods like a Chev / Ford "ball stud" rockers