You have an NPI motor, so you're limited to the Dorman et.al. manifolds, or you can install a Ford Racing PI manifold, but it's a little more involved. Unless you're planning significant mods, the Dorman will be fine. I have one on my 2000.
'03 Mercury Marauder (The Blackbird)
Trilogy Motorsports supercharged #61
Too many mods to list / Driveway Queen
'04 Grand Marquis LS Limited Edition (Spruce Green)
Daily Driver (Thanks, Adam!)
'00 Grand Marquis GS (Silver)
Rotted frame and broken transmission crossmember