360 heads on a LA 318 vs Magnum heads on a LA 318

PRH said
For me, it’s a tough sell to have someone spend money on heads that are visibly cracked.

If you’re lucky enough to have a pair of them that don’t have the exhaust seats sunk down into no man’s land, and can get away with a very minimal amount of machine shop servicing........that’s great.
But if they’re cracked, and they need some seats and/or some guides installed........ do you really want to spend the money for that on castings that are already cracked?

I guess I’d(meaning you) have to assess the actual condition of the magnums you have on hand before I decided if they were a viable option or not.

I would certainly take them apart and inspect them prior to use. I wouldn't put a bunch of money into them either. I do have all new valves for a stock magnum heads, springs too for that matter but they aren't the springs I'd be using anyways. I'd probably just buy new bare castings and put my new valves in them IF the magnum heads were the sure way I was going.