A few things:
These cars are usually less than 4500lbs with driver. Not as bad as people think.
Crownvic . net
Crown Victoria, Grand Marquis, Marauder, and Towncar is your friend
the Marauders and MK8s had 4 valve motors. Very different valvetrain and incompatible intakes.
high 20s is very acheivable in steady highway driving. I can do 23mpg in my brick-shaped carbureted 5.8L 1985 Crown Victoria. Similar weight, almost the same transmission (gearing changes a bit and yours is electronically controlled) and worse in every other concievable way.
The underside of these are VERY dirty. Lots of potential for experimentation there.
If there's a car reliable enough to offset fuel use with low maintanence costs, a Panther chassis (like our cars) is it.
If you want power, talk to Lonnie@ Blue Oval Chips or the good people at
ADTR | Your Panther Performance Specialist
They are the top two of a select group of shops that specializes in Panther chassis cars.
If you're interested in it, there is A LOT that can be done relatively cheaply to the handling of these cars
The transmission is the only thing that will directly swap over from the MK8 to the Town Car, and I'm not even sure about that (Lincolns used oddball trans lengths)
Junkyard parts and a relatively cheap tuner can be used to make them relatively quick, but if you want better than the 15s without nitrous, mileage-killing gears, and/or a barely streetable torque converter be prepared to shell out big money
The differences go beyond front and rear fascia for the Town Car vs. grand marquis and Crown Victoria. Again, Crownvic.net is your friend when it comes to sorting these things out.
Find out what rear gear you have. I don't remember the coding off hand, but getting the numbers from the tag on your rear axle cover or the area mark "AX" on the door sticker should give you what is needed to find out. You may have 3.27, 3.08 or even 3.55 rear gears as opposed to the highway 2.73s. That can be good or bad depending on your commute. Some report better in town mileage with gearing as aggressive as 3.73.
I love these cars and their anachronisms, and I hope you can find a place for it in your life. They are the height of comfort, as long as you don't have to park anywhere too tight!