Externally, the only thing that would distinguish the new piece from the old would be if the lower plenum looks shinier or newer than the upper plenum. Otherwise, they are identical. The rate of corrosion between the two would be a givaway. It the look equally corroded, then I would bet that it was not done.

1994 3.0L 4x4 pickup.
4.62 gears (4.22 stock), 33x10.5 BFG MTs. LSD rear. Five speed trans. 172K
Previously owned Mitsubishis:
1986 2.6L 4x4 Mighty Max, 1985 2.6L 4x4 D50
1987 2.6L Raider, 1989 3.0L Raider
1995 Montero SR