You have to pull your dashboard. I would highly recommend pulling the windshield also. This will really help you get a good fit. You must trim the front edge a lot, the bolt holes line right up with the metal tabs on the fox body. You also must trim the sides of the dash. You must trim the metal reinforcement bar in the back of the 94+dash. You also must cut and bend the bottom mounting tabs on the dash reinforcement. Next, in order to bolt the console up to it, you have drill the spot welds on the metal brackets under the carpet out of a 94-04 Mustang, and weld them into your fox. This is easy, but a lot of work if you have no experience with drilling spot welds of welding.
ANOTHER THING TO CONSIDER!!!! You must move your inside door handles back on your door and shorten the rod the the latch. Now you have a big hole in your door panel where the original handle went, and you must make a new one!! This would be time for a set of new panels from www.50resto.com I hope this helps. This would be a good winter project, because it will take days to figure out exactly how you want to go about this. I would not want to miss the last few good weeks we have of summer.