Open AT on q2406b


I am currently using the Open AT 3.1 which has built in 657c firmware in its IDE settings .
The q2406b that i am working with has 640 firmware pre installed.
Therefore i am guessing that in order to work with this Open AT version and download projects to the 2406b , i would need to add to my IDE firmware setting path the same files that i have for the 657c.

Are there any other changes that has to be done other the this in order to use this version and where can i get access to these 640 firmware version