I will present my reflection based on the Airbus A300-600ST Beluga and I suppose the reflection is the same with the Boeing B747LCF Dreamlifter:
The A300-600ST was built because its predecessor (the B377SGT Supper Guppy) was not large enough to transport future aircraft's large pieces. Those pieces are too large to be transported by train or by road.
But the A300-600ST's pieces must have been transported to build the aircraft. Some of the A300-600ST's pieces must be larger than the pieces this aircraft is designed to transport. So I'm puzzled because I cannot figure out how large pieces of this heavy transporter were transported to its assembly site. The same reflection goes with the B747LCF.