Pentaho Data Integration - Kettle- Update Identity Column in Microsoft SQL Server

For migration purposes I need to migrate existing ID's from my old database to my new table in MS SQL Server. I can truncate my table in MS SQL Server and then adjust my database connection in Pentaho to 'SET IDENTITY_INSERT tablename ON'. Then I am able to insert my ID's through a table output step, but I want to be able to UPDATE my existing ID without truncating my table in MS SQL Server. Could this be possible using Pentaho?