Lucky for you I have my 1984 Direct Connection Carroll Shelby's Mopar Chassis book handy!
Now, I just hope I'm not too late!!
Okay. The Axle Width Chart shows:
Standard Track : 70-74 E-Body 8 3/4": 60.7"
They have no measurements for Housing Flange to Flange.
Spring Seats Center-to-Center: 46.0"
Hope that helps! DON'T FORGET TO TAKE YOUR TAPE MEASURE WITH YOU WHEN YOU LEAVE!