See Mark Drake's (Product Manager Oracle XMLDB, Oracle US) response in this old post: ORA-31167: 64k size limit for XML node
The "in a future release" reference, means that this boundary 64K / node issue, was lifted in 11g and onwards...
So first of all, if not only due to performance improvements, I would strongly suggest to upgrade to a database version which is supported by Oracle, see My Oracle Support... In short Oracle 10.2.x was in extended support up to summer 2013, if I am not mistaken and is currently not supported anymore...
If you are able to able to upgrade, please use the much, much more performing XMLType Securefile Binary XML storage option, instead of the XMLType (Basicfile) CLOB storage option.