During your inspection you may find that the splines on the hub itself are rolled over, or sharp. This is a great indication that the hub is shot. I have several sets that are no longer suitable for use for this very reason. They engage and operate well, but sacrifice lockouts like it going out of style.
70's front lockouts were not Warns, they were Spicers, and are probably the toughest out there. Unfortunately they are 30 spline........
The DynaLoc front hubs appear to be the best on the market. Plus these Dynaloc hubs fail to lock, which is interesting enough.

Spicers with a Chebby style dial: