Which JBoss 7 version do you use?
There are some issues and you should compile the latest 7.x version from github.
What you need from EJB2, you need to provide a bit more information about your application.
I use JBoss 7.1.1,
the application running on jboss 5 using EJB2, we need to running it on JBoss 7.1.1 without change the EJB version
As 7.1.1 is an old version of AS it might have issues.
It depends on what components and features do you use.
It gets more complicated as more complex your application is.
In general there is no special configuration for the server, except you use CMP in this case you need to use the -full- profiles.
But depend on your application you need to add a jboss-ejb3.xml deployment descriptor and adapt some attributes in the DD.
So you need to be more specifiy