im thinking that most of the problem with the lunch box lockers is the clearance specs over time. it might be time to get some new side gear washers to bring them in specs again. with any metal to metal contact there will be wear and adjustment is needed over time.
mine was definitely not repairable with washers....the center pin was wallered out... i will take pics the next time my front diff is apart...
i think a normal person with a relaxed driving style the "lunchbox" lockers would last a long time on the street, you just have to keep off the throttle in the corners (its how i drive, fast in corners slow on straights lol)
is the detroit your running a true trac ?