Presently there are two conversion centres for the 747-400sf. Boeing has contracted TEACO in Xiamen, china to convert pax aircraft using a Boeing certified kit. All known customers have signed up with this programm. First aircraft to come off the line is planned for the 4th quarter 2005.
Bedek in Israel has an independent programm, so far without a known customer. They claim to have one order however.
SIA is contemplating a conversion line using Boeing kits as well.