Often I watch it on our website. Visually, I do not notice any difference. Maybe in the technical part they differ?

Search and ye will find: https://en.wikipedia.org/wiki/Ford_Crown_Victoria_Police_Interceptor 

98 models had chrome grilles and and the hubcaps in the picture below

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcS2cawBSmbdyWQVKcnOPpJOOtTFekEx2uJIvnAWEsg8HYR9xZCu

99-00 models had black grilles and the same wheels

https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcRDys75Ifa-73t2FQZp8Q94wwR-nCfTDHueWP2zmBNvM1zSEmNl

01-02 models where the first to have the new "honeycomb style grille" but still had the same wheels

https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcRsQcrwkIkc-86MdCmgRuX09MuOFUW83TipzF9zDMmdY-slvnFq

 

03-05 models got a new set of hubcaps ( and 05 models had a rear antenna)

https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcTraLAto0PkX8BZZW7oO5cgtF62Bk6w9qq59_WB5AF4dyU8Ffr2

06+ models again got new wheels

https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcQEprWrYjFrEr3AJT1eXpwqNu4i3y9R3kFmbmCKUG6kccfIEajpPQ

2010+ models got even bigger head rests and a different door trim i believe. they are also called p7b instead of p71

Here's a comprehensive list of every change that occurred on the Crown Victoria all the way back to 1992.

http://www.pontiacperformance.net/TechArticles/CV_Year-to-Year_Changes.html

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Aside from what has already been mentioned above,

The 1998-2002 models had different wheel center caps than the 2003-2011 models.

The 2003/2004 models had a steering wheel with the Ford logo actually in color as opposed to embossed like the 1998-2002 models. 

The 2005 model had a rear whip antenna added and changed the design of the steering wheel.

2006 dropped the rear whip antenna and got a new gauge cluster.

Edited August 18, 201510 yr by FCV96

My brother has the 2003 Model of the car. It's a good car V8, and haven't had any problems for a few years now.