The channel was replaced, trunnion was fine. They replaced just about everything, the top cover received new components. The entire build/upgrade ran about 10K. That was in 2005.
There was no DO at that time, it was USORD and they were still located near the old rodeo grounds north of I-80.
BTW, the current owner of the RIA Postie M60. Received the LMG in 1990 from a SOT in his area...
BTW, I would assume you got a new E4 mod0 topcover as well since an E4 cam arm won't fit into an original M60 topcover (or even into an E3 topcover).
In retrospect, perhaps a better deal than what you thought...