Locking your diffs really arent a good idea, unless your only driving in straight lines 95% of time. If you lock your diff the truck will always push into turns, not to mention the strain you put on the drive train.
But if you insist on locking your diff i would just put a liitle dab of JB weld in your diffs to lock them up permenently. An alternative to this would be to use some Team Associated green slime or HPI diff lube to to slow down some diff unspooling.