gen1 V6 have 8" front axles which are stronger than 7.25" 4cyl. axles (like your 87) they have lockers available.

I locker is FULL time 4wd(if both front and rear are locked). You may have noticed some time in your life than when a tire comes of the ground it spins like crazy and the that does have traction doesn't move. Well, a locker "locks" both axles and the wheels will turn in any situation unlike an "open" diff. You'll want it if you plan to wheel alot <img src="/forums/images/graemlins/kewl.gif" alt="" /> But, this is why you need the 8" diff. Lockers break axles with real big tires ~35"+
You WILL need lockout hubs with a locker or you will have horrible turning radius and tear wear.
some Gen2 rear ends 92-99?00 had optional airlocker which can either be open or locked. Better for the street when open and good for wheelin when locked. Those come on 9" and 9.5" rear ends which you will probably never break.

<img src="/forums/images/graemlins/kewl.gif" alt="" />