Anything past 30 and you're going to have to shave the intake mounting surface and use shorter push rods. It can be done, but money spent on them gaining a half point of compression might be better spent on different heads. The 308 castings are no better than your typical J head.
Engine Quest offers an iron Magnum head that can take an LA manifold for not a lot of money. Closed chamber and flow gobs better than the early factory LA heads.
You can reuse the 318 mounts on the 360. The passenger side is exactly the same and the driver's side can be shimmed with a longer bolt and washers. Either that or spring for a brand new set of Shumacher's.