La to Magnum parts list??

Looks like the power steering pump will be an issue if you run LA heads. The Magnum heads have bosses that the LA heads do not that are used to mount the pump.

Not running PS is a bit of an issue as belt routing seems to be difficult without the pump. Don't think it is impossible, it would fix the issue with the lack of bosses on the heads. Just saying that it seems like there are difficulties with it.

There is also the issue of the tensioner as it bolts to bosses on the head that are missing on an LA head.

I've seen pictures of a kit by Magnum Mopars where they built a mount to put the tensioner over the top of the water pump. This would solve both issues with the missing bosses, assuming you want neither AC nor PS.

Just a heads up.