no conversion
i did my initial on the 605 3 years ago and in my class there was a chap who was coming from the crj who was doing a FULL initial, and another guy from jaa-land who was coming from the 850 and he was doing an initial as well, and those are facts!! there is no, i repeat no cross-over conversion type course from crj to 604-605 other than taking a full initial.
hope this helps
baobab72