Matthew Pinsent and James Cracknell, the Olympic champions in coxless fours, are to form a four with Steve Williams and Josh West until Britain's final Olympic trials on 13-14 April.
The other half of the coxless four which won silver medals in the last two World Championships, Toby Garbett and Rick Dunn, will train in a pair.
Pinsent, going for his fourth Olympic gold, will stroke the four as he did in Sydney.
Pinsent and Cracknell were soundly beaten in the pair at the 2003 World Championships, while the four narrowly missed gold. The coach, Jürgen Grobler, has to decide which combination is likely to deliver his target of two Olympic golds in Athens.