Magnum vs la timing chain cover

Mounting pattern is not same. They are similar, but different, as seen in pishta's photo. The gaskets are different.
If you are running Magnum style heads, swap the timing cover and the rest is easy.
If you are running LA heads, just stick with V-belts or go with an aftermarket serpentine system. Someone on this forum previously suggested CVF racing, I think it was.