Magnum oil pan is rear sump, and interferes with K member. You need to use an LA type centre sump oil pan. Which opens the timing cover gasket can of worms, since there are no Magnum engines for cars (as OEM). It's on the magnum swaps.com site.
You need an LA oil pan; the Magnum oil pans (I don't know if they are the same between the 5.2L and 5.9L engines, but all Magnums were used on trucks only) will NOT fit in an FMJ, the sump will hit the K member.