Yep, had to open up the inside of the rotor like you did, and the inside of the crown vic backing plate. Didn't have to open it too-too much...just did it with a dremel. I asked a machine shop to do it but they weren't sure how they'd do it with the backing plate being all odd shaped and such. I got a fresh new bit for the dremel and went to town, didn't take too long to open them up.
I think I may have taken a pic or two during the process, but don't have them anymore

. But basically, mine looked like the above when I got it home from the junkyard, and when it was finished it looked shiny, but not as shiny as the above!! Here are the pics of the install. This was two years ago and this one went under my 96XJ, which at the time was on 31" ATs. It's currently on 32" MTs....and may be getting sold. I also installed an aussie at the same time, which I highly recommend!
And here is my other XJ 44 with 4.88s, a detroit, and still with drums!!
I've been thinking of switching the discs over to this XJ. The drums stop the 36s just fine. The only annoyance is that every time I go through some mud the brakes don't stop squeeking!!! I may convert this one over to discs also just to get rid of the squeeking!! I did the disc swap on the smaller XJ because when I pulled the axle from the junk yard one of the drums was kinda messed up.