I know that this is an older post but I thought that I should add to the information here. The Road King of any year is a great buy for what is a most unknown reason.
I have a friend who worked for HD dealerships all over but ended up in Baton Rouge,La. in the late 80's.
He was sent to several schools until he had his PHD in Harley Mechanics. He gave me some insider information about the Police Bikes many years ago and I have purchased and ridden only those models ever since. The information is not printed anywhere that I know of but it makes very good sense for the company.
My friend was at the factory for one of his schools when the instructor gave them this information.
Harley does a motor test and transmission test when they are completed and ready to install. They take the top 10% of the runs and reserve them for installation in the Police bikes. They want to make sure that only the very best completed bikes go to the various departments. Less or no break downs means nothing but the best PR for the MOCO. It keeps those sales at the top and not at the bottom where the company found itself during the bad years. They don't intend for that to happen again.
Being a former cop of many years I can tell you that the bikes take a real beating and they are ridden very hard on each shift. They do however keep them with the required maintenance schedules which is one way to make sure they keep going.
If you have a Police Bike as I do then you can rest assured that the drive train is one of the best to leave the factory.
This is not to say that if they are abused they will still keep going but they will take much more abuse than a good owner should give them.