found these pics from Airliners.net. never heard of the 747-4J6 cargo…

Its a 747-4J6(LCF), a conversion of a standard passenger 747-400 that will be used to move parts of the 787 from around the world to Seattle for assembly. The “J6” bit is just the Boeing customer number, indicating that the aircraft was originally built for (and was previously operated by) CAAC/Air China – there are many other 747-4J6 aircraft around, but only one has been converted into a 4J6(LCF). Boeing will eventually have three 747-400(LCF)s.

Andy