Just as an aside, why do you care if it validates against 1.3 if you're going to port it to JEE 5?
JEE 5 is pretty backward compatible with JEE 1.3.
Why not simply work towards getting your current application deployed in a JEE 5 container as is, and verifying its deploy against a JEE 5 container rather than being concerned whether it's compatible with a 1.3 container. At most you may have to tweak the descriptors, but a JEE 5 container should run your application just fine (of course there are always cross container nits and details that can get in the way outside of the spec itself).
At the end, you'll have your app up and running in the JEE 5 container and you can then proceed to incrementally port your app over. No reason to slam dunk and do the entire thing.
Just a thought.
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