Palsut, I don't think you've ever been in the backseat of a police car, so let me tell you, it's cramped. A Crown Vic isn't very spacious. I'm 6'2", and I had to sit sideways.
However, here is a side-by-side comparison between the Crown Vic & G8 for interior room. Also, I included the Dodge Charger, which I have heard cops say is way too cramped.
MSN Comparison *EDIT* Plus, the Crown Vic is grossly underpowered, both as a V8 and as an "interceptor." It makes less power than a stock GTP.