Well, it isn't really GlassFish that is 64-bit but rather the JVM that is runs on.
64-bit VMs are available from the regular Java SE download site @ java.sun.com, but I don't know how much testing has gone into GF on a 64-bit VM.
May I ask why you need a 64-bit stack?
A 64-bit heap (for caching of large data) sounds like the only time I would need 64-bit, but I might be wrong.
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