Sorry, I just read the top post in the forum and it appears as though I just use the oracle-persistence-service.xml.
Yes, we have simplified clustering considerably in 1.4.0.
One of the changes is there are no longer separate clustered and non clustered persistence config files.
I recommend you look at the 1.4.0 userguide, since a few other things have changed in clustering too (no more default router policy or message distribution policy).
Basically we have tried to make clustering easier to setup and configure.