I swapped a Detroit Locker into my 14BFF a few months back. This was on a 4.10 and down carrier.
Ordered new bolts over the phone through ECGS, asked them about the lock washer. They said they aren't needed, you are supposed to clean out the threads on the ring gear and use loctite with the new bolts.
I reassembled and torqued new ring gear bolts together with loctite and haven't had any issues.