You do know that la and and Magnum exhaust are the same correct? I mean the attachment point. You can put any La exhaust on the Magnum. either that or everything I've been told it's completely wrong...
Yes, the bolt pattern is the same, although the ports are slightly different. Ya gotta use the magnum gaskets with Magnum heads and you have to do some minor port grinding on the LA exhaust manifolds ( center 2 ports in particular ).