If you want a grand marquis or marauder headlights you need to swap the header panel, grille, bumper and lights to get good fitment.
If you want cheap marauder headlights, you can get grand marquis ones, throw them in the oven and open them up. You can take the chrome trim from the lens and rub it with soapy water and the chrome will rub off and become glossy black. Slap them back together. Voila marauder headlights.
I would just go with a clean pair of depo or tyc headlights and get clear corner lights. The corners yellow over time so you need to UV protect them with something