Hey, Being a MOPAR nut, maybe I can help a little.
I am pretty sure the '66 is a 4 door Belveder. If it is a #'s matching engine and car then it was ordered and at one time a police car.

Ma MOPAR came out with "440 Specials for police dept's only. You could order a 440 commando, or a 440 magnum for domestic use. Most of the magnums went into GTX's and such. Better performance heads and larger carbs were standard. Also back then "free flowing" exhaust.
The 440 commando went into pick up trucks and larger trucks at the time. You also will see them in some motor homes.
The 440 special was a 440 with the larger carb and free flowing exhaust , heavy duty suspencion, rearends, and trannies. Now I am not sure if they got the magnum heads or not with them. Check the front of the haeds. There will be a " X " marked on them. If so, then it had "magnum" heads as well.
There has a been a movement as of late of restoring and collecting old MOPAR cop cars.
As with anything...could be worth some money to the right person!

DCON