The 747 LCF (aka Dreamlifter) were built from passenger 747-400s, not former freighters. The subject aircraft were high time/low cycle aircraft. Boeing had four LCFs built, there are no current plans to build anymore.
The 787-10 will be built in at the North Carolina 787 plant, alleviating the need to move the longer fuselage sections of the -10 to Everett (as currently planned, the 787-10 center fuselage section is too long to fit in the LCF).