The Crown Vic/Grand Marquis/Town Car group are nearly the same. The Town Car is a little bit longer, most of that in the back seat. The best year for the Town Car for you is 96 (they were cheapened a little after that). Don’t buy any of these later than about 99, reliability began to decline. Now, the 25 mpg figure is only believable if you drove on a freeway at 55 or so. I go over 70 and got about 20-21. About 12 mpg in town.
Figure out how much you will drive and then how important gas is. Estimate your yearly expense if gas was $10 a gallon.
Insurance and repairs are much cheaper on these cars.
Rust has not been mentioned. It is very important, depending on where you live. Mechanical work is much cheaper than body work.