Have a look to [1] for migration issues.
If it was me I would upgrade to EJB3 as it's easier to handle and you have still the migration effort. Also EJB2 is running out of interest, I suppose there is less support for enhancements.
To map your JNDI names you should have a look into the subsystem 'naming'. You can add a <bindings> section and add individual aliases
<lookup name="java:global/Alias" lookup="ejb:app/modul/......"/>
[1] https://docs.jboss.org/author/display/AS71/How+do+I+migrate+my+application+from+AS5+or+AS6+to+AS7