It's hard to think of a better one.
Bullitt and To Live and Die In L.A. come to mind, but neither is as much based on a true story, at least to my understanding.
I suppose the case could be made that L.A. Confidential is also based on reality; it too is surely one of the best copy movies ever made.
“The Seven-Ups” with Roy Scheider is another good one from that era.
Think I’ll dig out all of these great flicks from the collection this weekend and have a cop film marathon.