Did a search and either I missed it or not much has been done on this? Anyone?
http://www.coolcats.net/library/parts.html -
"Mark VII panels can technically fit but will result in squeaking where the panel meets the dashboard, as well as less-than-perfect fitment."
That came from personal experience, too. I like them, nice panels, actually less complex and a little more streamlined than a lot of the Cougar/T-Bird panels. But you'll never not get them to squeak. Only other options would be to do some surgery on the panel by the dash area, which probably will create less than desirable results, but they can be recovered to look halfway decent. Or, swap out the dash to a Mark VII.
Did you try both styles? '84 - '89 and '90 -'92 are shaped different at the front due to the dash redesign.