ok most of the things i would like to do have probably been run into the ground, dug up, burned then buried again. But I would like to do some of these mods to make my car a little more fun to drive. I'm not looking to build a race car (as is evident by the 2.8l) so let me plug the list. Actually its just a couple right now.
just a couple things I can't find any clear cut answers.

I have put the 4:1 center diff mod on the list of possible mods in the future. but what I would really like to have some clarification on is how much of a total pain it would be to hang a 90 locking rear diff and housing into a B5 sedan. (not worried about the actuation of the locker) or a V8 Torsen and what the difficulties to each project would be. I am a capable mechanic and I'm not afraid to get elbow deep in sludge. and i have machining and welding experience too.
Thanks
plz don't comment on my grammar, I know it sux

 

plus im hand fabbing an exhaust from the manifolds back, what would be a good diameter to maintain proper back pressure as i think im going to go with a true duel exhaust all the way to the rear muffler and delete the mid muffler. Also i have an inexpensive source for some performance flowmaster Cats. would these suffice without throwing codes?