what rear is the most popular up grade

[jeremy canter]

just what the title says whats the best 8.8 center up-grade for a dayly driven cobra with some mild to heavy track use? I mostly drive highway mile's 16 miles to and from work but love the track > I need something with more grip than the stock rear > and while im in it doing gears I figure i'll do a new center too.
what your .02

 

[ninjastang125]

Ford unit rebuilt is the best peice. I race the crap out of mine and it has never let me down.