When I bought my 1991 XJ three years ago, the previous owner had a friend install a new heater core. He tried doing it without removing the dash and basically broke the front of the box off and then found out he had the wrong heater core. I bought it a few weeks before winter and pulled the dash and found out it was the right heater core and installed it. The problem is since the HVAC box is broken, the flaps that control the defrost, middle, and lower vents won't work.
I picked up a 1985 XJ for the axles and am wondering if the HVAC box is identical to the one in my 1991. Considering the work involved with pulling both dash panels, I don't want to find out the older one won't work.

 

As far as I know, they are. Everyting else seems to be the same