318 police?how can I tell

My '73 duster came with a '87 318 in it,supposedly a police motor. How can I tell? I think it has a small cam in it,and it does have a 650 holly,but otherwise appears to be stock. Cast iron intake,and exhaust mans. My '73 Dart Sport has a 360,eddy performer intake/carter afb perf. carb and headers. Both 321 r/e. The 318 will eat that 360 for lunch,and have room for dessert. I have a 340 bought for the duster,and I'm thinking of putting the 318 in the sport. Thoughts?
Dave Fair Grove,Mo(just north of Springfield)