Hee. I haven't actually "done" any rear disks yet. I don't care much for the Versailles rear, the technology is a bit dated and parts expensive. Search the Forum and find out what a lot of VMFers think about the Versailles swap.
Initially I planned to follow in AAloroque's foot steps. He used Cadillac brakes and it seems to have worked out very well for him.
http://communities.msn.com/aaronlaroque/reardiscsetup.msnw
I've decided to go with Lincoln Mark VII LSC rear disks, sticking with FoMoCo stuff. I've bought most of the parts required.
http://www.ultrastang.com/Ultrainfo.asp?Page_ID=14
Another option is to use the whole rear end from a 95 or newer Ford Explorer. The lug pattern is the same as the old Mustangs and you'd get low mileage bearings,axles,gears, etc in the bargain. I don't care much for the 8.8 rears and the disks are a little wimpy for my taste. I don't know if any VMFers have actually used one yet, but there's been lots of discussion.
I've looked at some Crown Vics but they didn't seem to me very suited to Mustang adaptation. Then again I've been rooting around rear disks for 2 years and just found out 2 weeks ago about the Mark 7 swap. I'm pretty sure the Crowns have a bigger bolt pattern, but then so do Aaron's Cadillac brakes. There seem to be more brake choices all the time.