RE: What posi unit?
For posi units, I know most guys will suggest the Auburn LSD or the Detroit True Trac. The Auburn is slightly cheaper than the Detroit. The Auburn also uses clutches, whereas the Detroit used gears, which supposedly are much more durable. Auburn is known for its dependabilty and quality though, so you don't have to worry about it breaking or anything. Hometheaterman runs an Auburn LSD, and he doesn't shy away from recommending it to anybody, so I am sure it's a fine unit. My stock LSD is tearing apart, so I will need to be replacing it soon. My choices are between these two, decision has not been made yet.