If your differential was never touched on your 03 GT
you have 3.27's they came with them from the factory.
FRPP 3.73's are the perfect street/highway gear in my opnion I would go with them if you do highway driving.
I purchased my gears on www.ebay.com and found a
good deal on my ring and pinion.I payed a professional
driveline shop 350 to install my ring and pinion.I supplyed the Royal Purple diff. fluid.
You have 3.27's and since you already know which gears you want, all you need to do is buy them and have a shop install them. I'd say pay someone to do it becuase if they whine you can always take it back
I would also have someone install them for you, it's one of the more complicated mods and you need a lot of tools that the average person doesn't have. Also, i would go with FMS gears, they seem to have the best rep.
I've been advised it's best to just rebuild the entire rear end (re-shim, re-bearing, new seals) while you're doing the gears for a few reasons..
- You're going to have everything out anyway
- Cheap insurance for a worthy investment
- Better to optimize the new set-up.
There are too many reasons to list as to why it's better. It's not absolutely necessary, but highly recommended... It'll cost you a little more, but to me, well worth it..