I manage two different sites for one company. Each site resides on its own server (Mac XServes, Apache 1.3, php 4., mysql 4.)

One of these sites is being converted to Drupal by another developer. There is some interaction between the two sites - scripts run on one may update a database on the other server or pull data from the database on the other.

I need to create a duplicate of one of these sites so that the other developer can run tests and make sure the interaction is working correctly. I am looking for any suggestions on a good way to accomplish this and what land mines I need to be careful of.

I know this is pretty generic request but any help would be greatly appreciated.