90 interior in a 84?

Don't forget the heater case too since the two model years are different ones. Also, is the 84 still carbed or swapped to EFI? If it's still carbed, then the wiring for the gauges will have to be figured out as well to make them work properly unless you put in aftermarket gauges. Other than that, I've swapped out an 83 conv interior with a 93 interior and it was alright. Don't forget about the quarter window issue as well.

Well, aftermarket gauges would certainly look better as well as read more accurately except that it raises the cost of the interior swap. Mustangs Unlimited sells an aluminum panel to replace the factory cluster and I believe Florida Mustang does as well.

you'll have to swap the 87-93 quarter windows too, or you'll have a big gap between the panel and the window.

fyi, the 90 is the wrong year to swap. the rear 1/4 panel pieces won't work.

the rear seats won't work either, nor will the rear seatbelts. ther front seatbelts will work, but for the rears, you'll have to use 79-89 belts unless you are into serious welding and drilling. use an 83-89 rear seat as well.

in 90, the front belt mounting locations are physically higher, this is why those big rear panels won't fit, unless you hack the panels to hell.

imo, the early four eye interior is the meanest and best interior of them all. If black is what you want, nearly all the black interior from the 79-83 models will swap in.

this swap is not as easy as it sounds. the dash swap is going to suck ass, the rear seats, seatbelts, and rear panels will suck too. you'll be alright with the carpet, front seats, etc etc

my bro wrote a real super nice, detailed article on interior conversions for fox body mustangs, should have ALL the information you'll want before embarking on this project, take the time to read this:

http://50stangs.com/techarticles/foxbodyinteriorguide.html