If you going the crown Vic route most you will find are retired taxis and cop cars. I would say engine hours matter way more than year specific crown vics as they are all essentially the same from the start of production to the end of the line in I believe was 2011. Could be wrong on that though. Only difference being minor tweaks here and there for suspension and other stuff like seats. Nothing much at all.

Eg car has 50k miles on odo but engine hours is 10k hours. You can equivalate 1 engine hour to around 30ish miles. So instead of having a 50k odo car, add it up and you have a 350k car. My buddy bought himself a police interceptor from 2008 a while ago, engine was "shot" but he ran the car anyway with misfire for 20k more miles lol. Easy boats to drive, easy burnouts/donuts (disclaimer I have property to do this on, don't be stupid) only thing is gas for these cars. Thing eats gas like crazy. 

Go with the Ford Crown Victoria.  Overall reliable, parts are readily available, fairly cheap, DIY-friendly, and plenty of space to work under the hood.  See post here for best years (the info. applies to the Crown Vic):

https://carkiller.com/scottykilmer/postid/18648/

Some issues to be aware of:

https://carkiller.com/scottykilmer/qa/ford-crown-victoria-manifolds/#post-17767

https://carkiller.com/scottykilmer/postid/90060/

https://carkiller.com/scottykilmer/qa/crown-vic-help-and-idle-hours/#post-91458

https://repairpal.com/problems/ford/crown-victoria

https://www.carcomplaints.com/Ford/Crown_Victoria/

Be sure to have a good, independent mechanic with a fancy scan tool like Scotty’s check it out before you buy (especially the transmission).