As far as the diff goes, Detroit lockers are not very friendly for street use. For traction, they are excellent and very durable, however they can be noisy and especially the occasional BANG you get when backing out of a parking spot and turning. You will swear someone just hit you.
I have used Torsen differentials in the past and they are great. No clutches, smooth engagement, very durable. They are expensive- the last one I bought was about $480. I wish they made one for the Jag (Dana) rear. Also, no friction modifier is necessary with Torsen diffs.
http://www.torsen.com/