You already have a Marketo connected to an instance of SFDC and want to switch to a different instance of SFDC.
This is not possible. Once you have connected your Marketo instance to an instance of SFDC, that connection cannot be changed. If you want to connect Marketo to a different instance of SFDC, you would need to contact your Customer Success Manager to have a new Marketo instance provisioned.
Who This Solution Applies To
Customers with a Salesforce integration