That M body police car that Dabney Coleman was driving sure took a beating, but just kept going on. I realize it is just a movie, so I woulnd't count on regular M bodies being able to continue that way, but it gives a lot of credence to the M bodies being tough cars.
I counted 6 M bodies (inlcuding the one Dabney Coleman was driving. A couple of Impala/caprice cop cars, and the bad guys were in a big Pontiac (Bonneville in the US, Laurentian/Parisienne in Canada).