It doesn’t take long to convert from EASA to FAA. First he needs to do the foreign license verification. Then he has to complete the ATP CTP course which will him allow to take the ATP written test. Thereafter he can do the Checkride in a Seneca or similar. If he prefers to do the Checkride in the A330 he would have to do an FAA type rating course since the FAA doesn’t accept the EASA type.