Hi Dan,
As is in Method there no way to move entries from the Existing Customer List to a Customer Contact List, you either have to manualy add the entries or you could do some customization and add a means to copy details from a Customer into a customer contact.
-MIchael
Michael Melo
Product Manager
Method Integration Inc.
Website: http://www.method.me
LinkedIn: http://www.linkedin.com/in/MichaelMelo