The nice thing about boxes is the general interchangeability for major body panels, with the exception of the Town Cars. It would take major modifications to make Town Car parts fit on a Crown Vic or Grand Marquis. I'm also only covering front end conversions. I will be referring to both models as simply Crown Victoria and Grand Marquis. I am well aware that the earlier models were LTD and the Crown Victoria was a trim level. The same theory applies to the Marquis. It will be easier for everyone that reads this if I stick to Crown Victoria and Grand Marquis.
Lets start with the fenders. The fenders are identical on the Crown Vic and Grand Marquis. The only differences being that from 1979-1981, possibly 1982, were that the Mercurys had louvers in the fenders. The Crown Vics never had the louvers. Older cars optioned with power antennas had the antenna located in the rear. I'm not sure what year the power antenna was moved to the front fender. I know my 1988 Grand Marquis has the power antenna in the front. The only other difference is that some cars were optioned with ditch lights, some weren't.
Now to explain the differences between the hoods. The Grand Marquis hoods stayed the same from 1979-1991. The Crown Vic had two different hoods. From 1979 to 1987, the hood was unique to the Crown Vic. From 1988-1991, the hood was the same one used on the Grand Marquis.
The header panels are the major noticeable difference between the Crown Victoria and the Grand Marquis. The Crown Victoria had 3 different header panels. There was the 4 headlight panel from 1979-1987. There was also a 2 headlight panel during part of this time frame. Lastly, there was the 4 headlight panel from 1988-1991. The 1979 Crown Victoria had clear lenses in front. After that, the lenses were amber. Again in 1991, the Crown Victoria received clear lenses. Moving onto the Grand Marquis, there was only 2 header panels. There was the 1979-1987 four headlight panel and there was the 4 headlight panel from 1988-1991. The grilles and hood ornaments changed throughout the years as well, though the focus of this article is not on those differences. The inclusion of the clear lenses on the Crown Victoria is due to the fact that these were one year only pieces and as such are exceedingly hard to come by nowadays.
The bumpers are different between the Crown Victoria and the Grand Marquis, though the mounts are identical. There are a lot of variations between the older bumpers on the Crown Victoria. The 1979 bumpers are unique in that they have 2 holes in the middle with plastic that matches the look of the grille. The plate holder sits in the middle of the bumper. There are differences in the plastic trim. Some cars had clean bumpers with no trim, some had trim going all the way across the bumper and some had little plastic bumpers. Some cars had trim and no bumpers, while others had trim and bumpers. After 1979, the license plate was moved to the drivers side of the car. In 1988 the Crown Victoria's changed to match the new header panel. The license plate was once again moved to the center of the bumper, and it had plastic trim that wrapped around the bumper.
From 1979 to 1982 the Grand Marquis had a similar slotted bumper to the 1979 Crown Victoria. Some of the cars with slotted bumpers had the license plate holder in the middle and some others had the plate holder on the drivers side of the car. I'm not sure why there is a variance with the same bumper. In 1988, like the Crown Victoria, the Grand Marquis got a new bumper. The bumper on the Grand Marquis is shaped a little differently than the Crown Victoria's bumper because the bottom of the header panels are different. The trim on the Grand Marquis bumper is thicker than the trim on the Crown Victoria's bumper. This is because the Grand Marquis has trim that runs the length of the car and the bumper trim completes the look. The Grand Marquis has little plastic bumpers like the Crown Victoria, but the Grand Marquis' are metal and plastic. The Crown Victoria's are just plastic. The little bumpers also sit right next to the plate holder on the Grand Marquis, where there is space between the little bumpers and the plate holder on the Crown Victoria's bumper.
Last but not least, we have the filler panels. On the 1979-1987 models, the filler panel was tucked in behind the bumper to cover the gap between the fender and the bumper. On the 1988-1991 models, the filler panel actually wraps around the top and sides of the bumper. The Crown Victoria filler panel differs from the Grand Marquis in that the Grand Marquis filler panel has trim to match the trim on the side of the car. The word Mercury is also stamped into this trim.
I would like to thank 87gtVIC and Brown Muscle for confirming there is no difference between hoods on the 2 headlight and 4 headlight models. At the time of my original post, nobody had yet confirmed whether or not the LTD S utilized a separate hood.