Tell ya what...
Instead of an Impala SS, look for a reired 9C1(police pkg) Caprice. The 9C1 has the engine of the Impala SS, but not the looks. Since it's police-spec, some components should actually be tougher.
The biggest deal of all is that 9C1s don't hold their value like the Impala SS. I've seen Impalas still oing for $12k in my area, while 9C1s are as low as $2k.
They have tons of torque, so you can probably drift one stock. I was trying to talk a friend into getting a 9C1, too.