The 57 Custom 2 door was widely used by many state police agencies across the country, as well as some major cities, including NYC. During the 50s, most state agencies actually did use the 2 door sedan for most duties.
Dave, I have an extensive collection of accurate police historical information regarding this time period; as to who used the 57, accurate markings for that time and equipment. I'd be happy to devote some time to insure this replica is authentic.
If Revell took the extra step to find the radio and gumball light, that's a good thing. Let's hope they don't stop there, there are many options for the cop car goodies, even back then.
EDIT: Just did a quick count...At least 25 states used the 57 Custom in the 2 door version for State Police/Highway Patrol duties, and a few more used the 4 door version. At least 8 to 10 of them have the decals readily available from the aftermarket or other kits. Another 6 to 8 have been done but are OOP and hard to come by.
Virginia SP: