Take a look at what will replace the Ford Crown Vic, for years a police standard. (Well, in some jurisdictions...)
And no 8-cylinder available, either.
How about a V-6 with a 6-speed transmission? Ought to get a pretty good top speed out of that.
One of the problems in police departments is the rarity of the high-speed chase. So, do all the cars have to be capable of running down the kid on the crotch-rocket or the robbers in the Charger? Many departments now prohibit high-speed chases. It's not that they want to let the other driver go; they just don't want to some innocent people trying to catch him.