I am going to show my Tamiya TT-01 Police camaro (1969) in an entertaining Police-car chase! If you want to see the chassis, the scale-parts for the body or the light-system, check out the video of my Police-Mustang:
f I may be so bold, what you need to do is to modify the light bar a bit and to also make it look like a classic light bar as well as having rotating discs or simply be a double dome light bar.
And have the siren in a horn on the middle of the vehicle and to make more 1960s or 1970s style decals for your vehicle instead.