The latest version of CADWorx can create a CAESAR II file of type 4.40, 4.50, 5.00, or 5.10. This is designated by setting the CAESAR II Version variable in the CADWorx configuration file. I'm not sure if you can go all the way back to 4.20.
(You realize that from a "Piping Code" point of view, your CAESAR II is "seriously" out of date - right?)
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Regards,
Richard Ay - Consultant