I have a complete 3.5:1 F-series IRS diff for sale. These aren't exactly the easiest things to come by. To my knowledge this is the highest (factory or otherwise) diff ratio available to suit an F-series.
Just the thing if you'd like your Supra/Celica/etc to be more efficient and rev less on the highway. Also increases your top speed for those who are that way inclined and are blessed with the horsepower to do it!
The other good thing is for people who have a useless first gear due to an engine conversion! Having 3.5 gears will dial out some of that wheelspin and allow you to get out of the hole better!
I'm moving house, so I wouldn't mind ditching some of my unnecessary stuff... but there's no urgent need to sell - if I don't I'll still be fitting it to my car!
Asking $275, open to offers if you're prepared to show up cash in hand a pick it up.