Oh, I forgot to add, you can easily tell if you have the sure brake option. look under the hood just to the right of the radiator (passenger side) and if there's a complex looking canister device that looks like this illustration: http://imperialclub.com/YearbyYear/1973/FSM/Chassis/html/05-080.htm It's the presure regulator for the rear brakes. you have surebrake, I think all instrument clusters have this window, it's just not lit if they don't have the option. Jack