what would be my best option to get true 2 wheel drive without replacing the entire axel housing? Prefer limited slip if is do-able.

90 3.9 auto/2wd

 

LSD doesn't always get you the 50/50. The best option for not to much money is a Powertrax lockright. It is a full locker which will give 50/50, automatic locker. I have one, it is simple to install and totally worth it.

The only negative thing is on a dead stop and turning the locker will stay locked and light throttle is needed so you don't slip the tires.

For me it was worth it. But for some it might not be worth it. http://www.richmondgear.com/powertrax/lockright.html