While trying to find out where the rubber raft is in the A-20 I found this photo archive: http://www.nationalmuseum.af.mil/photos/media_search.asp?q=A-20&page=1
I don't know if there is a raft in the A-20. There is a "Gunner's Life Preserver" in the waist, but I am not sure if that could be used as a raft with room for all crew men.
Is the raft behind the cock-pit? "...so we removed the five-man life raft from the shelf behind the cock-pit." I did not know that. It's from Wreaking Havoc: A Year in an A-20
By Joseph W. Rutter
Here is a photo of an A-20 1/48 model, the yellow part is the raft: