Every M body sold to law enforcement got an 81/4 and suregrip. rear sway bar too.
That is not an 100% accurate statement. I would say "
most law enforcement" got the 8-1/4" differential and rear sway bar/larger front sway bar setup - but not all.
I would also say very few police cars came with limited slip. Police cars (for the most part) are bid upon from the big three (back then). The police dept would give a "min specification" and sometimes a "would also be nice specification" for cars to be bid upon. If limited slip wasn't mentioned in the "min specification" sheet, then it didn't get added - and it was rarely mentioned.
I know for a fact that police cars - that maybe 5% came with limited slip - and maybe fewer than that.
I have even seen some F/M-body police cars (for Tulsa (OK) Police Dept) that came with 7-1/4" differentials and no rear sway bar. They did come with the modified door strikers and other body "police" changes - but otherwise was a plain Jane, F (or M-body). Most police departments were on a tight budget.
HeHe, I even remember being chased by the Tulsa Police, and it took him two plus miles to catch me, in his Ford Fairmont I6 car - and I wasn't even trying to run from him. I had a rolling stop and thought no one was watching. I pulled over thinking police - flashing lights, you gotta pull over to allow them to pass (two lane road) and he got behind me. I wasn't even speeding the entire time.
Most Highway Patrols and (US) Federal law cars came with all of the goodies.
BudW