I have an 8 1/4 rear and I am going with 3.55 gears. What exactly needs to be changed? I found a few kits but some have bearing included and some don't. Which should I get?
http://www2.partstrain.com/store/details.../M92C825IK.html
http://www2.partstrain.com/store/details...92R825RMKT.html

I'd get the one with bearings included if you do not have the resourses to remove the old bearing from the pinion!

if you have never setup a rear i would suggest not.watch someone who is knowledgeable at doing it first.

And buy quality pieces. In R&P kits you get what you pay for.

I probably should have mentioned I am not doing this myself. So I should stay away from the kit and by better parts? Thing is, I don't know what to buy

Is a shop doing the work or a buddy? If a shops involved I'd go with what they're familiar using. I don't see what ring and pinion brand you were looking at. The first kit shows bearings that aren't in it. The 2nd has timkens in it.
My last "hey buddy" job was on an '08 Mustang and I begged him to get everything from Randy's Ring & Pinion, and recommended factory gears. Too expensive! So he ordrerd parts from Summit and Jeg's and got 4:10 Richmond gears that you can never get all the noise out, shims that don't resemble anything that came out of the car, and I had a question about the new posi unit that neither place could answer. Everything turned out ok and he's happy but that little whine on coast would bug me in a new car with a v-6!