Two posts, finance director and head of procurement, have been newly created to cover both the FSA and MHS, while the agency is also advertising for a director of strategy and resources and an HR director.
The formal merger between the FSA and MHS began in July following critical reports on inefficiencies and duplication of services. Staff numbers at the two agencies have been reduced by 15% since the merger.
The FSA had one director looking after finance, resources and procurement, but the new FD role will just oversee the finances of the MHS and FSA.
A new £65,000 a year head of procurement role has been created, while responsibility for resources moves to the strategy director role, which is being advertised at £110,000 a year.
The FSA's director of strategy left last month to join the Department for International Development, while the HR role has been filled on an interim basis since Brian Davies left the agency in October 2008.
The arrangements for the merged bodies are expected to be finalised by April 2010, with a further year allowed for transition to the new structure.
"Excellent progress has been made on integrating the FSA and MHS corporate service functions," said FSA chief executive Tim Smith.